Slow Cooker French Onion Soup

Ever order French onion soup at a recipe only to get a bowl with so much cheese you can’t tell whether you ordered soup or a grilled cheese sandwich? Yeah, me too. That’s why I love to make slow cooker French onion soup at home. I can control the cheese. I like mine on top of lightly crusted sliced baguettes. Like crunchy cheese croutons. Perfect on a cold day, this soup is packed with fantastic onion flavor.

Slow Cooker French Onion Soup

I like to add a bit of beef base to my slow cooker French onion soup to give it just a bit more beefy flavor. Although it’s completely optional if you use a good homemade beef broth. I felt it could use a little help in the beefiness flavor department.

Also try my slow cooker spicy kielbasa cabbage soup and my slow cooker meat lovers chili.

Slow Cooker French Onion Soup
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5 from 1 vote

Slow Cooker French Onion Soup

Perfect on a cold day, this soup is packed with fantastic onion flavor.
Course Main
Cuisine American
Keyword crockpot, onion, slow cooker, soup
Prep Time 15 minutes
Cook Time 8 hours 45 minutes
Total Time 9 hours
Servings 8 servings
Calories 325kcal
Author Mike


  • 6 tablespoons unsalted butter
  • 4 large yellow onions sliced thin, rings separated
  • 1 tablespoon sugar
  • 2 cloves garlic minced
  • 1/2 cup cooking sherry
  • 7 cups beef broth
  • 1 tablespoon beef base optional
  • 1 teaspoon kosher salt
  • 1/4 teaspoon dried thyme
  • 1 bay leaf
  • 8 slices French bread or 16 slices of a thin baguette
  • cheese A mix of shredded Gruyere, Emmental, Parmesan and Mozzarella cheeses


  • Melt the butter in a large pot or Dutch oven over medium-high heat.
  • Add the onions and saute about 10 minutes or until translucent, stirring often.
  • Sprinkle with the sugar, stir and reduce heat to medium. Cook 30-40 minutes or until soft and lightly caramelized.
  • Add the garlic, stir and cook 2 more minutes.
  • Stir in the sherry and cook until evaporated, stirring and scraping up any yummy bits on the bottom of the pot.
  • Transfer the onions to a lightly greased slow cooker on low.
  • Stir in the broth, beef base, salt, thyme and bay leave.
  • Cover and cook 8 hours.
  • Place bread pieces under the broiler to get lightly browned. Sprinkle with cheese and place back under the broiler until the cheese is melted.
  • Serve soup in bowls topped with a slice of the cheese bread (or 2 slices if using a small baguette).


Calories: 325kcal | Carbohydrates: 45g | Protein: 11g | Fat: 10g | Saturated Fat: 6g | Trans Fat: 1g | Cholesterol: 23mg | Sodium: 1555mg | Potassium: 324mg | Fiber: 3g | Sugar: 7g | Vitamin A: 266IU | Vitamin C: 6mg | Calcium: 65mg | Iron: 3mg

Nutritional values are approximate.