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Best Crockpot French Onion Soup

This crockpot French onion soup is so easy and delicious, it will literally blow you away! It’s warm, hearty, and perfect for those chilly winter evenings!

July 14, 2021
French Onion SoupPhoto By Canva
Difficulty Hard
Servings 8 people
Preparation 15 mins
Cooking 360 mins
Total 375 mins



  1. Add the quarter-moon onion slices to a 5-quart or larger slow cooker. Season with salt, butter, oil, and a generous amount of freshly ground black pepper.
  2. Set the crockpot to low and cook the onions for 12 hours or overnight until soft and dark golden-brown in color.
  3. Add the balsamic vinegar and reduced-sodium beef broth to the pot. Stir it in and cook for another 6-8 hours on low. Taste the soup and add more salt and pepper if required. If using brandy, also add it around this time.
  4. Now add a rack to the upper third of your oven and heat it up. While you wait for your oven to heat up to 350°F, ladle the soup (with the onions) into oven-safe bowls and arrange them on a rimmed baking tray.
  5. Prepare the bowls for baking by adding a slice of toast and about ⅓ cup of shredded Gruyère cheese to each bowl.
  6. Then place the baking tray with the soup bowls into the oven and bake for about 20 to 30 minutes, or until the cheese is completely melted.
  7. Once the cheese has melted, change your oven's settings to broil for about 2 to 3 minutes or until the cheese is bubbling and browned.
  8. Remove the tray of bowls from the oven and let everything cool for a couple of minutes. Then, serve your crockpot French onion soup with toasted baguettes, chopped shallot, or fresh onion and enjoy.
Nutrition Facts
Serving Size 1 French Onion Soup
Serves 8
Amount Per Serving
% Daily Value*
Protein 10.72 g21.4%
Total Fat 11.67 g15%
Cholesterol 17.86 mg6%
Sodium 1688.98 mg73.4%
*The % Daily Value (DV) tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.


  • If the soup turns out watery or thin, simmer it gently in a saucepan over the stove top for 10-15 minutes, or until the broth reduces and the soup reaches the desired consistency.
  • While this French onion soup recipe uses yellow onions, sweet onions are also great for this recipe. You can also use a combination of red and yellow onions, as per your preference.
  • For this recipe, you must slice the onions into quarter-moon slices. You can do this using a knife, mandolin, or even a food processor.
  • This best onion soup recipe involves no stirring or checking while slow cooking, so do not hesitate to leave it cooking without supervision overnight.
  • Slow cooking your onions for 12 hours with butter and salt is likely to leave your home smelling like cooking onions. Instead, do this step in the garage or on the porch to avoid this.
  • Slow cook your soup for another 6-8 hours, as cooking longer will help intensify the flavors of the soup. This recipe is flexible enough that the soup can be left cooking for quite long if your slow cooker holds moisture well.
  • If your slow cooker doesn’t hold moisture well, wrap a towel over the lid to minimize the steam escaping.
  • Bake the soup after topping to evaporate excess moisture and thicken it.
Rate This Recipe

This Classic French onion soup recipe is honestly the best onion soup recipe to exist. Rich, filling, and comforting, this real simple French onion soup recipe can be made in a crockpot with minimum supervision, making it the ideal recipe for those looking for a low-effort dinner.

What Is French Onion Soup?

French onion soup is traditionally made with beef broth and onions and topped with toasted bread slices and cheese. The soup's roots stretch back to Roman times, but it didn’t gain the form we know today until the 17th century. The soup was then enjoyed as a hearty traditional dish until the 1960s, where it rose in popularity due to the increasing interest in French cuisine.

What Is The Difference Between Onion Soup And French Onion Soup?

The difference between onion soup and French onion soup lies in the ingredients. Red or yellow onions are used in French Onion Soup , while in onion soup white onions, red onions, shallots, and leeks are used. It calls for beef broth, while onion soup can be made with any broth and doesn't call for any type of alcohol. Not to mention French onion soup is preferred with Gruyere, Emmental, and Swiss cheese, while onion soup uses cheddar cheese.

How To Make French Onion Soup?

Traditional French onion soup is made by cooking the onions and broth on the stove top and then baking, but healthy slow cooker French onion soup can be made by cooking the onions in a crockpot for 12 hours, cooking an additional 6-8 hours after adding the broth, and then baking for 20-30 minutes after topping with bread and cheese.

What Kind Of Cheese Is On French Onion Soup?

Gruyere cheese is generally considered the best cheese for French onion soup, but you can also use Fontina, Emmental, Mozzarella, Gouda, Jarlsberg, or Provolone. Other Swiss cheeses like L'Etivaz, Sbrinz, Scharfe Maxx, and Engelberg Cheddar are also considered great alternatives to Gruyere.

Is French Onion Soup Vegetarian?

While the butter, beef broth, and cheese mean this French onion soup recipe isn’t vegetarian, you can easily make vegetarian French onion soup by substituting with vegan butter, vegetable broth, and vegan cheese.

What To Serve with French Onion Soup?

For an irresistible hearty dinner, serve this simple French onion soup with salads, steaks, scallops, and baked salmon. French onion soup also pairs beautifully well with dark chocolate desserts like tarts, mousse, and cakes and can also be served with dry and fruity wines like Gamay, Pinot noir, Viognier, etc.

Here are our delicious recipes that you can serve with French Onion Soup:

Recipe byPetite Gourmets

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