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Slow Cooker French Onion Soup

  • Prep Time: 15 minutes
  • Cook Time: 6-8 hours (low); 3 hours (high)
  • Servings: 6 - 8
  • Course: Soups & Salads

French onion soup is flavorful and hearty. Simply prepare the soup in a lined slow cooker to warm and allow flavors to meld, and you’ll have a comforting and delicious French Onion Soup.

Reynolds Kitchens® Tips

Reynolds Kitchens tip

Get the same flavorful and hearty soup but from your slow cooker! Line your slow cooker with a slow cooker liner to ensure those sweet, caramelized onions don’t stick. Plus, there’s no sticky mess to clean up when you are done!


  • 5 tablespoons unsalted butter
  • 5 large yellow onions, sliced (1/4-inch-thick slices)
  • 1 tablespoon brown sugar
  • 3 sprigs fresh thyme
  • Pepper, to taste
  • 3 tablespoons all purpose flour
  • 1/4 cup soy sauce
  • 2 cups chicken stock
  • 2 cups beef stock
  • 1/2 pound grated Gruyere cheese
  • 1 loaf Sourdough bread (optional)


Step 1

LINE your 5- to 6-quart slow cooker with a Reynolds® Slow Cooker Liner.

Step 2

MELT butter in a large pot over medium heat. Add the onions, brown sugar, thyme and pepper and cook, stirring frequently, until the onions are very soft and caramelized, about 25 minutes.

Step 3

ADD flour, stir to evenly coat onions.

Step 4

Remove from heat and stir in soy sauce.

Step 5

ADD caramelized onion mixture into slow cooker. Add the beef and chicken stocks, cover with lid, set slow cooker to high heat and cook for 3 hours, or until soup is hot.

Step 6

REMOVE and discard thyme sprigs.

Step 7

LADLE into bowls and top with cheese. Serve with sourdough bread (optional).

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