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classic french onion soup recipe

Homemade French Onion Soup in Slow Cooker Crock Pot

Family dinners cooked in a Crock Pot can be so delicious and full of flavor. This homemade French Onion Soup can easily become your staple for family meals.

Course Soup
Cuisine French
Keyword crock pot, French Onion Soup, slow cooker, soup
Prep Time 10 minutes
Cook Time 12 hours
Total Time 12 hours 10 minutes
Servings 6
Author Celebrate Woman


  • 3 lbs yellow onions peeled and sliced into quarter moons
  • 4 Tbsp unsalted butter melted
  • 2 Tbsp olive oil extra virgin
  • 2 tsp kosher salt
  • 12 cups beef broth or chicken or vegetable if you like
  • 2 Tbsp balsamic vinegar
  • Black pepper to taste

To Serve

  • 2-3 slices of toasted baguette per bowl sliced, herbed, toasted
  • cup Gruyère cheese per bowl grated
  • Chopped green onions and herbs optional


  1. Season the onions. Place the onions in a 5-quart or larger slow cooker. Stir in the butter, oil, salt, and a generous amount of pepper.

  2. Cook on LOW for 6-8 hours. Cover and cook on the LOW setting overnight until the onions become dark golden-brown and soft.

  3. Stir in the broth and balsamic vinegar.

  4. Cook on LOW for extra 6 hours. Cover and continue cooking on the LOW setting for about 6. This is flexible. As long as your slow cooker holds moisture well, you can cook the soup for hours. Longer cooking will only intensify the flavors. Taste and season with more salt and pepper if needed.

  5. Portion the soup into oven-safe bowls. Arrange a rack in the upper third of the oven and heat to 350°F. Ladle the soup and onions into oven-safe soup bowls.

  6. Top with toast slices (store-bought or homemade, see my post) and shredded cheese. Top each bowl with a slice or two or three of toast and a generous quantity of shredded Gruyère cheese, about 1/3 cup per bowl (depends on how big the bowl is).

    Place the bowls on a rimmed baking sheet into the oven for about 30 minutes.

  7. When the cheese is melted and looks a bit toasty, remove the soup bowls from the oven and top with fresh green onions and herbs if you wish.