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!
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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!
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).
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 Chicken Pot Pie Soup – Comforting and creamy.
- Crock Pot Cabbage Roll Soup
- Slow Cooker Chicken Enchilada Soup
- Crockpot Chicken Noodle Soup – Great for leftovers!
- Slow Cooker Cajun Bean Turkey Soup Recipe
- Easy Crock Pot Ham and Potato Soup – Favorite recipe!
Equipment
Ingredients
- 3 large white onions sliced
- 3 tablespoons butter
- 64 ounces beef broth I use reduced sodium
- 1 tablespoon Worcestershire sauce
- 1 clove garlic minced
- ⅓ cup dry sherry
- 4 sprigs fresh thyme or 1 teaspoon dried thyme
- 1 bay Leaf
- 8 slices French bread * stale or dry is best
- ¾ cup shredded Gruyere cheese
- ½ cup shredded Emmental cheese
- 6 tablespoons shredded Parmesan cheese
Instructions
- In a large non-stick pan, cook onions, and butter over medium-low heat until golden and caramelized. (About 20 minutes).
- Once golden, add to the slow cooker along with the remaining ingredients except for bread and cheese.
- Cook on low for 6 to 8 hours.
- Remove and discard bay leaf and ladle the soup into bowls. Top with dry bread slices and cheeses. Broil 2 to 3 minutes or until cheese is melted and browned.
Video
Notes
Nutrition Information
Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.
Course Dinner, Lunch, Soup
Cuisine American, French© SpendWithPennies.com. Content and photographs are copyright protected. Sharing of this recipe is both encouraged and appreciated. Copying and/or pasting full recipes to any social media is strictly prohibited. Please view my photo use policy here.
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Outstanding recipe, bursting with rich delicious flavor!
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?
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.
Holly – I don’t understand why you would cook three large onions in the slow cooker but only use half of them. why wouldn’t you just put one and a half onions in the slow cooker? Is it because if you’re cooking them overnight, you need more bulk and a smaller amount would overcook?
Yes! You need 3 lbs of onions to properly caramelize in a slow cooker overnight but that is more than necessary for this recipe.
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.
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.
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.
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?
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 ½ to ¾ full.
Out of curiosity, would it be possible to add some sort of meat to this soup and it still come out alright?
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!
Absolutely!!! Beef stew would be amazing!!
I used this recipe and cooked a beef roast in the soup to make French dip sandwiches with, because in my opinion dipping them in French onion soup is ten times better than au jus. It required a little more work (spooning off the congealed proteins on top) but turned out absolutely amazing!
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.
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 :)
Merry Christmas Elaine!
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!
Yes, that would work just fine. It’ll taste great as the flavors have a chance to blend.
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
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!
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.
That sounds like a delicious idea Gael! You will have to let us know how it turns out.
I’ve made this recipe 4 times in the past 2 weeks . Bringing it to Christmas Eve dinner tomorrow! It’s delish!!!!
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 haha
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……
Thanks for sharing James!
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?
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.
Looks great!
I hope you enjoy the soup if you try the recipe Cathleen!
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 !!!
I am so glad you enjoyed this french onion soup Sarah!
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.
Thank you for sharing your tips on halving the recipe, so glad you loved it Kaylee1
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.
Such a great tip Chris, thank you for sharing!
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.
You’re welcome, and thank you!
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.
I’m so glad your family loved this Rachel! Love the idea of trying different cheeses, thank you for sharing!
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.
I’m so glad you love the soup Libby. The cheese is amazing!