Slow Cooker French Onion Soup

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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. And the aroma that filled the house while this soup was cooking in the crockpot was absolutely amazing. My stomach was growling all day long!

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 mine could use a little help in the beefiness flavor department. I used a store-bought beef broth which, though good, needed more flavor for sure. If I’d used a better brand (I admit it, I was being cheap) I could’ve skipped the base.

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



  • 6 tablespoons unsalted butter
  • 4 large yellow onions sliced thin, rings separated
  • 1 tablespoon sugar
  • 2 cloves garlic minced
  • ½ cup cooking sherry
  • 7 cups beef broth
  • 1 tablespoon beef base optional
  • 1 teaspoon kosher salt
  • ¼ 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.

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