Slow Cooker French Onion Soup

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Slow Cooker French Onion Soup is one of our favorite meals to come home to! As with any traditional French onion soup, this recipe features a beefy broth loaded with caramelized onions and herbs and topped with an amazing Gruyere cheese topping!

a bowl of French onion soup with cheese and thyme garnish with text


Crockpot French Onion Soup

French Onion Soup is one of my husband’s all-time favorites. It’s the perfect meal for any soup lover!

For me it’s all about the bread and cheese…  all soaked in that rich herby onion broth and then broiled until the cheese gets all hot and bubbly. Scooping up the first bite of that ooey gooey cheese is like a little taste of heaven.

While French Onion Soup is good, I do think that a good broth takes a long time to develop great flavor which is something I love about this recipe.

In this recipe, the onions and broth have the chance meld in the slow cooker all day long creating a rich and flavorful soup.  Not to mention, I’m a huge fan of slow cooker meals because I love coming home to dinner ready to go!

It just seems to make the evening run that much smoother, at least in my house with activities, homework and soccer practices!

closeup of a bowl of French onion soup with cheese and thyme garnish with a bite out of it

Why do they Call It French Onion Soup?

French onion soup actually originated in France in the 18th century and has been a traditional soup of France ever since.  This soup is most often served as a starter, however, we love to enjoy it (with extra bread and a salad) as a meal.

How do you Make French Onion Soup from Scratch

To make french onion soup completely from scratch you’d want to start with your own homemade broth or stock. While I often make chicken broth from scratch for this recipe I usually use a lower sodium store-bought broth.  Either will work just fine.

Caramelizing the onions does take a little bit of time but it’s totally worth the effort.  You want them translucent and golden without browning or crisping them so low and slow heat is the way to go with these!  You don’t have to stir them constantly but you do want to make sure they aren’t cooking too quickly.

While I caramelize them on the stove top for convenience, you can actually caramelize them right in your slow cooker too but it does take 8-10 hours!  If you get them started the night before, you can wake up to caramelized onions, add the remaining ingredients and you’re good to go!

How to Caramelize Onions in the Slow Cooker

Combine 3lbs sliced onions, 1/2 cup unsalted butter and 1/2 teaspoon salt.  Stir and cook on low 8-10 hours.  (You would need half of these onions for this recipe but can add more if you like. You can freeze the other half to add to mashed potatoes, casseroles, soups and more). (Note you do not need brown sugar if you use this method, the onions have enough natural sugars).

overhead of a bowl of French onion soup with cheese and thyme garnish

What is the Best Onion to Use in French Onion Soup

When making French onion soup, you’ll want an onion that will caramelize well and have the right amount of sweetness.

I find using regular white onions provides the best results as sweet onions can overpower the broth and tend to create a soup that is too sweet.

If you happen to have only sweet onions on hand, I would suggest eliminating any sugar from the recipe.

What kind of cheese is best for French Onion Soup?

The bread and cheese topping is one of my favorite parts of this recipe.  Using Gruyere and Emmental cheeses really make this dish amazing, however, you can substitute mozzarella/ parmesan/ swiss if it’s all you have on hand.

I love to ladle this into bowls, add the cheese and broil, however, you can simply place the bread & under a broiled on a pan and add it to your bowls if you prefer.

Serve this French Onion Soup with a side salad and some extra bread for a delicious dinner!

More Crockpot Soups You’ll Love

Slow Cooker French Onion Soup with cheese on top
4.94 from 62 votes
Review Recipe

Slow Cooker French Onion Soup

Prep Time 20 minutes
Cook Time 6 hours
Total Time 6 hours 20 minutes
Servings 8 servings
Author Holly Nilsson
Course Soup
Cuisine French
Slow Cooker French Onion Soup is one of our favorite meals to come home to! A rich beefy broth loaded with caramelized onions and herbs and topped with an amazing Gruyere cheese topping!


  • 3 large white onions , sliced
  • 3 tablespoons butter
  • 2 tablespoons brown sugar
  • 64 oz Beef Broth (I use reduced sodium)
  • 1 tbsp Worcestershire sauce
  • 1 clove garlic , minced
  • 1/3 cup dry sherry
  • 4 sprigs fresh thyme (or 1 tsp dried Thyme)
  • 1 Bay Leaf
  • 8 slices dry french bread
  • 3/4 cup Gruyere cheese , shredded
  • 1/2 cup Emmental cheese , shredded
  • 6 tablespoons fresh parmesan cheese

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  • In a large non-stick pan, cook onions, butter and brown sugar over medium low heat until golden and caramelized. (About 20 minutes).
  • Once golden, add to the slow cooker along with remaining ingredients except bread and cheeses.
  • Cook on low for 6-8 hours.
  • Remove and discard bay leaf and ladle the soup into bowls. Top with dry bread slices and cheeses. Broil 2-3 minutes or until cheese is melted and browned.

Recipe Notes

If you don't have dry bread, slice your loaf and dry it in the oven at 300 degrees for about 5-7 minutes. Cool completely.

Nutrition Information

Calories: 368, Carbohydrates: 44g, Protein: 17g, Fat: 12g, Saturated Fat: 7g, Cholesterol: 33mg, Sodium: 1348mg, Potassium: 303mg, Fiber: 2g, Sugar: 6g, Vitamin A: 360IU, Vitamin C: 4.4mg, Calcium: 282mg, Iron: 3.1mg

(Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.)

Keyword slow cooker french onion soup

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collage of a bowl of French onion soup with cheese and thyme garnish, one with a bite out of it
close up of a bowl of French onion soup with cheese and thyme garnish with text


two pictures of french onion soup

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Holly is a wine and cheese lover, recipe creator, shopping enthusiast and self appointed foodie. Her greatest passion is creating in the kitchen and making deliciously comforting recipes for the everyday home cook!

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Recipe Rating


  1. I’m still confused about the onions in the slow cooker. Am I supposed to cook all three onions in the slow cooker and then after they are caramelized, remove half?

    1. You can caramelize the onions on the stovetop as written in the complete recipe. If you’d prefer, you can also caramelize them in the slow cooker overnight the day before making the soup.

      If you use the slow cooker method, you will have more onions than needed for this recipe so half of them can be frozen for another use.

  2. Can you freeze this soup? It’s just me and this will make a large amount. I also used Beef stock because I need low sodium and it was lower than the others.

    1. Yes, this soup can be frozen. Cook as directed and ladle into individual servings. You’ll want to thaw in the fridge overnight and heat on the stove (or in the microwave) before adding the bread and cheese.

  3. Wow wow wow this was amazing. My partner is a vegetarian so we just subbed veggie stock for beef broth. We also used apple cider vinegar in place of sherry.5 stars

  4. What size crock pot do you use for the full recipe? If I need to adjust for a smaller recipe, should I also adjust the cooking time?

    1. I use a 6qt slow cooker. You can use a smaller slow cooker if you’re making a smaller portion, I would leave the cooking time the same. You’ll want to ensure your slow cooker is 1/2 to 3/4 full.

    1. I’ve only made the recipe as written Lolly, but I think you could add some meat and it’d taste great! Let us know if you try it with meat!

  5. I am a 94 year old widower and do all my own cooking in my condo. I have a 1 1/2 and 4 1/2 crock pot that I enjoy using. I especially like the 1 1/2 slow cooker.

    1. I am a 17 year old who loves to cook and I’m very excited to try this recipe for Christmas brunch! Merry Christmas Carl :)

  6. If I pan carmelize the onions In pan and cook everything in crock pot all day, can I put crock in fridge overnight and plug back in the next day? Will it taste just as good, or better? Thanks!

    1. I cooked the onions overnight and I’m ready to start the soup. Am I supposed to include the juice or drain the onions? Also, I don’t have sherry. Can I use white wine instead? Thanks

      1. Hi Deb, if there is a lot of juice you can drain some off but it should be fine to leave in (and will add a yummy flavor). As for the sherry, other readers have substituted it with white wine with great results, so it should work well!

  7. Very good recipe … Simple and well organized.
    Going to make more onions, this next time.
    Also, trying two or three types of onions, as
    I only used sweet white ones, the first batch.5 stars

  8. I’ve made this recipe 4 times in the past 2 weeks . Bringing it to Christmas Eve dinner tomorrow! It’s delish!!!!5 stars

  9. The recipe is delicious. But the warning about the smell is REAL! I caramelized the onions overnight in my slow cooker. To me it smells good but when I got to work the day after everyone told me I smelled like food. My jacket and bag smell so much! I’ll know for next time haha5 stars

  10. Do not add the sugar. Makes it way to sweet.
    I would also suggest to brown the onions in the stove top then put them in the crock pot……

  11. I have made this recipe before and I normally use a yellow onion, and it has been amazing! I decided to try the white this time. I use the crock pot method for caramelization, and they didn’t turn out as well. Are you suppose to add the brown sugar to the crock pot when using the white onions?5 stars

    1. Sorry to hear that Kelli. You shouldn’t need to add the brown sugar when caramelizing white onions in the slow cooker so I am not sure what went wrong.

  12. Best turn out yet!!! After letting the onion simmer overnight I seperated the onions from the juice and let it cool so it wouldn’t have so much oilthank you !!!5 stars

  13. I loved this recipe, it was easy to make. I caramelized the onions the night before, then added them to the pot that morning, and it worked out fine for me. If you half the recipe, you can make it in a 2 quart crock pot. Overall, it was super tasty and it smelled like prime rib while the soup was cooking, so that was a plus.4 stars

  14. I have a well stocked kitchen, but rarely keep sherry, or cooking wines on hand. I have a quick substitute that I learned from a pressure canning French onion soup recipe. These secret ingredient is…(drum roll)…..1-2 tsp of bold steak sauce. Yes…you read that correctly! It adds a rich flavor that works well with all the ingredients and depending on brand, gives a hint of a smokey flavor. You can even add if with cooking wine, but use sparingly. I suggest adding 1 tsp and let it cook add 1/4 tsp at a time until it suits your taste. I’ve made this recipe a few times now and we love it. I have used sherry, but the steak sauce substitute is our favorite.5 stars

  15. Your Slow cooker french onion soup recipe was delicious. It was my first time to make this soup, ever. My family is a huge fan of french onion soup too. It was so easy to make. Thanks.

  16. We just finished eating this wonderful onion soup. Made according to your recipe except I used marsala wine, and sharp cheddar cheese because that’s what I had . Came out great. My husband’s comment “you’ve outdid yourself ” I guess that says it all. Thanks Holly for a super recipe.5 stars

  17. I made this months ago and I am preparing to make it again. It was a huge hit last time and, now that hot soup weather is back, we are looking forward to enjoying it again. The Gruyere and Emmental cheese combo is genius. Soooo good. Last time I did the stove top caramelizing. This time, I will be doing the slow cooker method.5 stars

  18. Amazingly delicious. Everyone loved it! I caramelized 3 large yellow onions on the stovetop for 45 mins. Then added everything but the bread and cheeses to a pot and simmered for 4 hours on stovetop. When ready to eat, I laid 6 crostini on top of broth and added gruyere, parmigiano reggiano and pizza blend and broil for 10 mins. Will make whenever I have to use up a bunch of onions.5 stars

  19. Made this a bunch of times but never same twice. I used white, yellow, and sweet onion. This time I used sweet onions a lot more butter and 1/4 cup xabernet sauvignon wine and was absolutely amazing.5 stars

  20. Thanks for the easy, no fuss recipe. In my personal taste, it was a little too sweet and the condensation from the crock pot lid made the soup watery. After the six hours, I transferred the soup to a stock pot and boiled it down a bit. Still sweet, but not as watery. I will definitely make this again, but with less brown sugar and on the stove. Other than that, good color, good amount of onions and thyme. Thanks again!3 stars

    1. If you put a large piece of heavy grade aluminum foil on top of pot and then the cover, the condensation will go onto the foil. Make sure to fold the edges of the foil up, and remove cover as little as pssible.5 stars

  21. All ingredients are perfect except garlic…French onion soup does not include garlic at all…garlic is vastly overrated as an ingredient because it kills the taste…

  22. Just finished having the French onion soup. It was unbelievably delicious 
    Gave some to our daughter for work and my husband has not stop thanking me and telling me how delicious it was, wants me to make it again tomorrow night
    I used croutons and sliced Swiss cheese, it was so hot the soup melted the cheese so I didn’t do the broiling part . Thank you for the recipe5 stars

  23. If I cut the recipe in half, will it fit in a 2qt crockpot? It’s just me in my house, and I only have a small crockpot.

  24. Would love to make this but do not need that much! Way too much! How would I cut it down? Sounds do yummy!

    1. White and yellow onions are a little different. White onions tend to have a sweeter flavor than yellow onions. They are often used interchangeably in recipes.

  25. Wow Holly, thank you for writing this crock pot recipe. I actually don’t like onions in food and was recently convinced of its goodness. I’m traveling right now so I can’t try this out. Will be sharing with my friends, thanks.

  26. Hi! I soooo love this! Made this last night only thing I did different because I told my kids it’s onion soup they went blaa was I chopped up 3 lb of chicken thighs and put it in with the onions and the rest of they ingredients ! It came out so hearty and heavily! !! The family wants me to make this more!!! For the people who were worried about the Sherry how about alcohol content I bought cooking Sherry at the supermarket for $3 it does at such flavor!!! for the cheese I used freshly grated three cheese blend from my supermarket it had parmesan Asiago and Romano. I had the soup and soup Crocks put the bread in in the cheese on top and had them broiled in the oven till the cheese was brown and crispy! I highly recommend this recipe5 stars

  27. Hi Holly,
    I love French Onion soup so I’m trying your recipe in the crockpot today. I just have a question. When I cook the onions on the stovetop with the butter and brown sugar, do I add the juice that was created from the butter and brown sugar to the crockpot with the onions ? 5 stars

  28. This was my first time making French Onion Soup and I am extremely pleased! Even my husband had a second bowl and he’s not had French Onion Soup before. I could not find Emmental cheese (not even sure what it is) but it tastes great without it. The ingredients blended well and the flavor rivals restaurant soups. Definitely a winner for a cool 20° night on Texas…or anywhere!5 stars

  29. This is soooooo good. I do up a large slow cooker FULL of onions then freeze half to make it again in a couple of weeks,5 stars

  30. Made your soup with red onions and cooking sherry which has salt in it, then used the low sodium beef broth. Fantastico! Will be making it again this winter. Thank you for sharing.

  31. I’m a french onion soup addict and a bit of a snob to boot. This is the best onion soup EVER! I caramelized the onions in the slow cooker and used all of them in the soup. Totally awesome!

  32. I used salted butter and ommitted salt. Took 8 hours in my slow cooker to get onions translucent and golden. I use cooking sherry. Delicious. Kathleen R. Calgary Akberta5 stars

  33. I used 3lb of onions and carmelized them in the slow cooker overnight. My slow cooker only took 8 hours to get them translucent and golden. I used salted butter and did not use salt. Cooking sherry works very well.
    Delucious. Kathleen R. Calgary, Alberta

  34. Hi Holly
    I am making your french onion soup for dinner today….not going to change anything except going to use 1/3 cup of white wine instead of sherry. I will let you know how I did..thanks Theresa

  35. I used up the last of my red onions from this summer’s garden and made the recipe plus about a half amount more. I pre-caramelized the onions as you recommended and added them to the ingredients already warming in the crockpot. I recommend revving up the broiler before you ladle the soup into bowls, already on a sheet pain, and assemble the tops.
    The soup tasted like I had slaved all day but was incredibly easy to make. SO yummy on this snowy day!5 stars

    1. I have only tried this as written. If you try making the recipe with chicken broth, please let us know how it works out for you!

  36. I made this recently and it was SO easy and delish! I ended up buying jarlesburg cheese instead of gruyere cheese bc it was cheaper. I will make this again for sure! 

  37. Made tonight & it was very good! Thank you! Just took longer then recipe said to caramelize onions. I added more garlic cloves, one extra onion & used Gruyere & Swiss cheese! 

  38. Just a suggestion for anyone who doesn’t have oven proof bowls. When you put you bread in the oven to dry/toast, when it’s the way you want it, simply top the bread with your cheese(s) and broil til browned and melted, then using a spatula move your bread onto the soup in your regular bowls.

    You can also make a confining ring from an old but cleaned can or other metal bottomless ring of any shape so the cheese doesn’t spread out too far, if that’s a problem for you. This also works with croutons, homemade or store bought!

    I hope this idea is helpful to someone since some of us don’t have the space or money for special oven proof bowls, or if you aren’t sure if yours IS oven proof!.

  39. Sensational meals, that aren’t expensive or hard to prepare. We will try one tonite. Thanx for these great recipes.

  40. Hello Holly, thank you for this article.

    Recipes make life easy and when resources like this are available, it just make healthy eating inviting.

  41. Hi Holly,
    I’m making this soup as I type. I’m using the crockpot method to caramelize the onions and noticed that there is no mention of the brown sugar from the original ingredient list, but there is an addition of salt. When I add the rest of the ingredients in the morning do I add the brown sugar then out just omit it altogether?
    Thanks, Sandra

    1. Sorry for the confusion Sandra, the brown sugar helps the onions in the pan to caramelize a little bit quicker. I’ve found making them in the slow cooker, you don’t need the extra sugar. I’ve updated the post.

  42. I made this today!! Souper good! I made it exactly how it was written. I give it an 8 out of 10. Next time I will add a little more splash of cooking Sherry for richness and I will cut up 6 onions. 3 Just was not enough for me. I’m so happy with this recipe and so grateful you posted this!! Bon Appetite!!4 stars

    1. I am so glad you liked it Mel! I like the idea of a little more sherry. I will have to try that next time I make it!

  43. Hello, I noticed in the carmalized onion recipe you called for 3lbs, but in the recipe for the soup you said 3 large onions. Is it really only 3 onions if you do the stove top carmalizing?

    1. That’s correct, you need to have quite a few onions in the slow cooker so they caramelize properly. You will only need about half of them for this recipe.

  44. I carmelized my onions in the slow cooker the night before. Just turn it on before you go to bed (or sooner if you have to be at work in the morning). Add the rest of the ingredients and your good to go. You can always turn your slow cooker on warm if you’re not ready to put it in the oven yet. Waking up to the smell of carmelized onions had my mouth watering for dinner all day! Served this with Quiche and a salad

    1. I made this recipe last night. Made enough that I could share it with ailing friends. We ALL loved it. I caramelized my onions on the stove pretty easily and let the broth and all cook for about 4 hours. I will make this again and again and again. Awesomeness!

  45. Just confirming…. After you caramelize the onions for 8 hours in the slow cooker overnight then I add all the other ingredients, do I still cook for another 8 -10 hrs?

    1. If you caramelize the onions overnight in the slow cooker and then add the other ingredients, you would then cook the soup another 8 hours before serving.

  46. Just a wonderful recipe. Made several times. A must on cold days. I fry the onions low and slow in a cast iron frying pan.

  47. I have this in the crockpot now !! I bought sherry cooking wine at the grocery store . Is that the same as dry sherry??? I don’t want to mess this up!!!

  48. Good morning.
    I’m so anxious to try your soups, especially the French onion. I’m confused about the amount of onion. One place it says 3 pounds and another place it says 3 onions.
    I saw so many others to try also
    Thank you

    1. You would cook more onions if using the slow cooker version of caramelizing them however you will only use half of them in the recipe using that method.

      If you are caramelizing them in a pan, you will need 3 large onions.

  49. Can you tell me how many carbs are in this soup without the bread? Looks delicious but I’m on a low carb diet.

  50. When it comes to cooking with wine, I always shy away from it, because I am totally ignorant when it comes to picking wine for cooking! I never know what wine to use, so can I leave it out? Thank You!

    1. You can leave it out but it really does add nice flavor. Cooking sherry is sold in the grocery stores near the vinegars and olive oils and there are only usually a couple of brands to choose from.

      For whites, I use an inexpensive bottle of dry crisp white such as a Pinot Grigio or Sauvignon Blanc.

    1. The sherry adds a lot of flavor to this recipe. If you have it on hand I would definitely suggest adding it.

  51. Made this tonight & it was amazing! I followed the directions as instructed. Wouldn’t change a thing it was so damn good!!!

  52. Would any type of onion work? Could I use Vidalia? Looks great, making it for dinner tonight and hoping I don’t have to run to the store.

      1. Your print button doesn’t work. Very annoying because Your recipes sound the best.
        I use a computer or iPad and can’t carry that to the grocery store or put on the counter
        while I cook. I promise I would not steal or sell your recipes.

  53. Thanks for the recipe. We love French Onion soup. I did try the recipe, though, and the brown sugar made it too sweet. I will leave that out next time.

  54. You can carmelize the onions in the slow cooker, then added the rest of the ingredients and continue to cook. Delish

    1. While it would change the flavor of this soup, you could try a little bit of white or red wine, dry vermouth, or brandy.

  55. My BFF & I love French onion soup. Will be having her for lunch Thursday and im gonna make your recipe. One ? Though. Do you think it would be possible if I carmalized the onions with the brown sugar the night before & then warmed them in the microwave the following morning before adding them to the crock pot ? Just looking to save a little more time in the morning if possible.

      1. Thank you. Couldn’t make it thursday so its in the crock pot as we speak. Can’t wait to taste it. Will out you know.

    1. Carminlized Onion and Brown sugar with butter only in crock pot 8 to 10 hours before putting in liquids?? How to do that especially caramelized??

  56. Your recipe is exactly what I am looking for. I can try making a new delicious dish for my family. Thank you for your recipe