Rating: 4.5 stars 4.6
403 Ratings
  • 5 star values: 298
  • 4 star values: 74
  • 3 star values: 26
  • 2 star values: 4
  • 1 star values: 1

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!

Recipe Summary

30 mins
4 hrs 45 mins
5 hrs 15 mins


Original recipe yields 8 servings
The ingredient list now reflects the servings specified
Ingredient Checklist


Instructions Checklist
  • 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.

  • 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.

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

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

  • 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.

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


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

250 calories; protein 11g; carbohydrates 17.5g; fat 14.7g; cholesterol 37.6mg; sodium 595.9mg. Full Nutrition