Slow Cooker French Onion Soup


This slow cooker French onion soup is ridiculously easy to make, mainly since it cooks in a slow cooker! After it's been simmering all day, you come home to an amazing aroma and a fabulous meal for a cold winter day. You do not have to caramelize the onions; you can melt the butter in your crockpot, stir in the onions to coat, add the remaining ingredients, and cook. However, caramelizing the onions makes for a much, much better soup!

Prep Time:
30 mins
Cook Time:
4 hrs 45 mins
Total Time:
5 hrs 15 mins


  • 6 tablespoons butter

  • 4 large yellow onions, sliced and separated into rings

  • 1 tablespoon white sugar

  • 2 cloves garlic, minced

  • ½ cup cooking sherry

  • 7 cups reduced-sodium beef broth

  • 1 teaspoon sea salt, or to taste

  • ¼ teaspoon dried thyme

  • 1 bay leaf

  • 8 slices of French bread

  • ½ cup shredded Gruyere cheese

  • cup shredded Emmental cheese

  • ¼ cup freshly shredded Parmesan cheese

  • 2 tablespoons shredded mozzarella cheese


  1. Heat butter in a large, heavy pot over medium-high heat. Add onions; cook and stir until translucent, about 10 minutes. Sprinkle onions with sugar; reduce heat to medium. Cook, stirring constantly, until onions are soft and caramelized, at least 30 minutes. Stir in garlic and cook until fragrant, about 1 minute.

  2. Stir sherry into onion mixture; scrape the bottom to dissolve the small bits of browned food. Transfer onions into a slow cooker and pour in beef broth. Season with sea salt; stir in thyme and bay leaf. Cover and cook on Low for 8 to 10 hours or on High for 4 to 6 hours.

  3. Preheat the oven broiler about 10 minutes before serving. Set an oven rack about 8 inches from the heat source.

  4. Arrange bread slices on a baking sheet; broil until toasted, 1 to 2 minutes per side.

  5. Lightly toss Gruyere, Emmental, Parmesan, and mozzarella cheeses in a bowl. Fill oven-safe soup crocks 3/4 full with onion soup and float a bread slice in each bowl. Top each with about 2 tablespoons cheese mixture.

  6. Place filled bowls onto a baking sheet and broil until cheese topping is lightly browned and bubbling, about 2 minutes.

    a handled bowl of soup with bubbly browned cheese on top
    Michael Di Roma


If you like, put all the soup components — soup, toasted bread, and cheese mixture — out on the table and let people make their soup! This seems to be the favored method when I host a craft night. People can make their own decisions about what they want in or on their soup!

Nutrition Facts (per serving)

250 Calories
15g Fat
18g Carbs
11g Protein
Nutrition Facts
Servings Per Recipe 8
Calories 250
% Daily Value *
Total Fat 15g 19%
Saturated Fat 9g 44%
Cholesterol 38mg 13%
Sodium 596mg 26%
Total Carbohydrate 18g 6%
Dietary Fiber 2g 5%
Total Sugars 6g
Protein 11g
Vitamin C 6mg 30%
Calcium 197mg 15%
Iron 4mg 21%
Potassium 334mg 7%

* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

** Nutrient information is not available for all ingredients. Amount is based on available nutrient data.

(-) Information is not currently available for this nutrient. If you are following a medically restrictive diet, please consult your doctor or registered dietitian before preparing this recipe for personal consumption.

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