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 in bowl with crock pot
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Crockpot French Onion Soup

Crockpot French Onion Soup is one of our favorite meals. A rich beefy broth loaded with caramelized onions and herbs, topped with an amazing Gruyere cheese topping!
Prep Time 20 minutes
Cook Time 6 hours
Total Time 6 hours 20 minutes
Servings 8 servings
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  • 3 large white onions sliced
  • 3 tablespoons butter
  • 2 tablespoons brown sugar
  • 64 ounces beef broth (I use reduced sodium)
  • 1 tablespoon Worcestershire sauce
  • 1 clove garlic minced
  • cup dry sherry
  • 4 sprigs fresh thyme (or 1 teaspoon dried thyme)
  • 1 Bay Leaf
  • 8 slices dry French bread
  • ¾ cup Gruyere cheese shredded
  • ½ cup Emmental cheese shredded
  • 6 tablespoons fresh Parmesan cheese shredded


  • 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 the remaining ingredients except for bread and cheese.
  • 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.



No Dry Bread? Slice the loaf and dry it in the oven at 300°F for about 5-7 minutes. Cool completely.
4.97 from 219 votes

Nutrition Information

Calories: 367 | Carbohydrates: 44g | Protein: 19g | Fat: 12g | Saturated Fat: 7g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 3g | Trans Fat: 1g | Cholesterol: 34mg | Sodium: 920mg | Potassium: 648mg | Fiber: 2g | Sugar: 7g | Vitamin A: 361IU | Vitamin C: 4mg | Calcium: 270mg | Iron: 3mg

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

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French Onion Soup with text


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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 Nilsson is the creator of Spend With Pennies, where she creates easy, comforting recipes made for real life. With a passion for nostalgic flavors and simplified techniques, Holly helps busy home cooks create delicious meals that always work. She is also the author of “Everyday Comfort,” which promises to inspire even more hearty, home-cooked meals.
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    1. A common meat to add to French Onion Soup is beef chunks. But I think any meat that you prefer would work well in this recipe.

  1. This was a great recipe. I visited Montreal, Canada for the first time this past fall and fell in love with French onion soup. Before this, I’ve only had French onion soup from a down-under chain food restaurant and wasn’t really into it.
    I really liked that the recipe’s author talked about making caramelized onions in the crockpot. She had a note about not needing to add extra sugar if you use this method or if you use sweetener onions. My tastes are more on the savory side versus sweet, so I didn’t add any extra sugar. I cooked the onions in the crockpot for 10 hours overnight and in the morning added the other ingredients and let the soup cook for seven hours. After this time, I ladled the soup in these tiny All Clad ramekin/soup pots. I did dry out a French baguette in the oven as the author noted and let it rest for about 20 minutes. The cheese I used was hand shredded provolone and Gruyère. I also used Sauvignon Blanc wine in place of sherry and was nervous that the flavor would be off, but the soup still came out amazing!5 stars

  2. Giving 4 stars because I followed the recipe but somehow the broth was very bland. Had to doctor it up a bit. Maybe I did something wrong?4 stars

    1. Did you make sure your onions were caramelized and golden before moving to the next step? That adds a lot of flavor to this recipe. You can also add as much or as little seasoning as you like when cooking. So you may just prefer to add more into your recipe!

  3. Excellent flavor! I used Vidalia onions and one yellow onion. Use the slicing blade on the food processor to save time and tears. Next time I would caramelize maybe 1-2 more onions and reduce the sugar if using a sweet onion to start with. Vidalias are so watery and took a long time to cook down. Will definitely make this one again.5 stars

    1. I haven’t personally tried making this recipe on high, but I think it would work just fine. I would reduce the cooking time to about 3 hours.

  4. My son LOVES french onion soup so we tried this recipe together. Followed it almost exactly – used a pinch less dried thyme based on another review, used reduced sodium beef broth per author, and couldn’t find Emmental cheese, so just used the other two cheeses in recipe. We caramelized the onions on the stove, instead of the overnight method.
    The soup was very thin and watery. We used 7 cups of white onions (3 large), – maybe they were especially watery. It took 45 minutes to caramelize on med-low heat. The soup needed salt, so next time use regular beef broth, and I recommend cutting down to 48 oz. Maybe increase to 1 1/2T Worcestershire sauce, and reduce to 1/4t dried thyme. Even the bread was instantly soggy and we dried the French bread in the oven at 300 degrees for 7 minutes as in the Author’s notes. We are willing to try it again with our adjustments, but not anytime soon.

    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.

  5. Thank you so much for this recipe. It was absolutely amazing. I’ve always been too intimidated to make this soup for myself. It brought me back to a little French restaurant my mom used to take me when I was younger5 stars