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Ready to try the best French onion soup recipe in the world? All you need is a slow cooker, cooked onions and beef broth to make this easy soup recipe.

Slow cooker French Onion Soup Recipe

After his first bite of this soup, my husband declared that it was the best French onion soup recipe in the world.  And then he said it three more times so I can safely say that this is indeed a killer onion soup recipe.

What makes it even better is that it's basically a hands off recipe until just before serving.  So haul out that slow cooker and get ready to taste the best French onion soup recipe in the world!

Slow Cooker Caramelized Onions

The base of this soup recipe really is the onions.  You need a good amount of caramelized onions and the best way to cook them is in your slow cooker.  Check out how I cook onions to a nice brown, caramel color in my slow cooker.

Slow Cooker Soup Recipe

Once your onions are cooked, you simply add beef broth and flavorings.   I added in red wine, garlic powder and Worcestershire sauce, but those are optional.

Add the broth to the slow cooker where the onions cooked and set the soup on low. The longer it cooks, the better it gets. Cook it anywhere from 1-12 hours.

French Onion Soup

When the soup is ready, it's time to prep the bowls.  French onion soup is served with a slice of hearty bread and cheese on top.

I used some leftover sourdough sandwich bread from making Sourdough and Sausage Tuscan Egg Bake for breakfast.  I cut the slices in half so they'd fit squarely on the top of the bowl. Toast the bread to firm it up.

Easy French Onion Soup Recipe

Everyone uses a different cheese for the top of French onion soup. Truly, gruyere cheese is the best, but it's also really expensive. So feel free to use provolone, swiss or even mozzarella.

Put the bowls under the broiler until the cheese melts and then serve immediately.

And if you're going to be making this recipe a lot, you may want to invest in traditional soup crocks!

The Best French Onion Soup Recipe in the World


The Best French Onion Soup Recipe in the World

Serves 6-8     adjust servings


  • 1 batch of cooked onions
  • 8 cups of beef broth
  • 2 Tablespoons dry red wine (optional)
  • 1 Tablespoon Worcestershire sauce (optional)
  • 1 teaspoon garlic powder (optional)
  • Bread for each bowl
  • Cheese (gruyere, provolone, swiss or mozzarella)


  1. If you cooked the onions in a slow cooker , just add all the other ingredients to the same crock. Otherwise, place all ingredients in the crock of a 5-6 quart slow cooker .
  2. Cook on low for anywhere from 2-12 hours.
  3. To serve:
  4. Lightly toast bread slices. Ladle soup into bowls and top with the toasted bread. Top the bread with desired cheese. Broil the soup until the cheese is melted. Serve immediately.
Nutrition Facts
Serving Size
Amount Per Serving As Served
Calories 102kcal Calories from fat 8
% Daily Value
Total Fat 1g 2%
Saturated Fat 0g 0%
Transfat 0g
Sodium 733mg 31%
Carbohydrate 15g 5%
Dietary Fiber 1g 4%
Sugars 4g
Protein 9g

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

Calories 2000
Total Fat Less than 65g
Sat Fat Less than 25g
Cholesterol Less than 300mg
Sodium Less than 2,400mg
Total Carbohydrate 300g
Dietary Fiber 25g
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