Slow Cooker French Onion Soup

4.50 from 2 votes

Mix up a healthy batch of this traditional favorite!

Classic onion soup gets its flavor from richly caramelized onions in this slow cooker French onion soup recipe that will make a delicious starter at your next dinner party. When simmered in the slow cooker all day, it leaves your stovetop free for other courses of the meal, and produces a soup that is rich in flavor and nutrients.

4.50 from 2 votes

Slow Cooker French Onion Soup

This classic soup is prepared in the slow cooker, making it easy to make and super scrumptious.
Cook Time 6 hours 40 minutes
Total Time 6 hours 40 minutes
Yield 6 people
Serving Size 0.75 cup
Course Dinner, Soup
Cuisine Universal
Author SkinnyMs.


  • 2 tablespoons olive oil
  • 2 tablespoons butter
  • 1 sweet onion large, thinly sliced
  • 1 yellow onion large, thinly sliced
  • 2 garlic cloves
  • 1 teaspoon thyme
  • 1/2 teaspoon sea salt
  • 1/2 teaspoon ground black pepper
  • 6 cups beef broth
  • 4 slices whole-wheat bread thick
  • 4 slices provolone cheese


  • Heat the olive oil and the butter in a large skillet. Add the onions and cook over low heat, stirring often, until caramelized and browned, about 30 minutes.
  • Transfer to slow cooker pot, and add the garlic, thyme, salt, pepper, and broth. Cover and cook over low heat for 6-8 hours.
  • Before serving, toast the bread and preheat broiler to high heat. Ladle the soup in and lay a slice of cheese over each bowl. Broil until the cheese is well browned and serve.

Nutrition Information

Serving: 0.75cup | Calories: 304kcal | Carbohydrates: 18g | Protein: 16g | Fat: 18g | Saturated Fat: 9g | Cholesterol: 29mg | Sodium: 324mg | Fiber: 3g | Sugar: 5g |
SmartPoints (Freestyle): 11
Keywords Low-Carb, Slow Cooker, Vegetarian

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  1. Pinned! This looks delicious. I love French Onion Soup, and better yet if it can be made in the slow cooker. I will be trying this soon!

  2. Question… you put the bread on top of the soup and then the cheese and broil?? Sounds good….just not sure what to do with the bread after I toast it! The picture looks like the bread is in the bowl under the cheese…Thanks!

  3. This recipe looks very good, except for one thing: provolone cheese. The cheese to use on French Onion Soup is Gruyere. Imagine using American cheese in lasagna…

    1. Just a slight exaggeration on the American cheese comment. If you don’t want to pay $25-30/lb for real gruyere (the cheaper stuff isn’t worth using), a good substitute is provolone with some Parmesan to salt it up. Some even use Swiss or a combo of the 3. It’s very common.

    1. Great question, Holly. Use dry thyme for this recipe (not ground). However, if you prefer fresh you can substitute 2 teaspoons fresh chopped thyme.

    1. Lisa, Most grocery stores have “sweet” or “Vidalia” onions. These onions are not as strong as regular yellow or white onions. The have a milder taste. 🙂

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