Crockpot French Onion Soup

Crockpot French Onion Soup is a rich, savory classic made easy with the help of a slow cooker. Caramelized onions simmer slowly in a flavorful beef broth, creating a deep, comforting soup that’s finished with toasted bread and gooey melted cheese. It’s the perfect meal for chilly days or cozy nights at home.

Why You’ll Love This Recipe

This Crockpot version of French Onion Soup takes all the effort out of a traditionally labor-intensive dish. The slow cooker does the heavy lifting, developing rich flavor over time without constant attention. With minimal prep and maximum comfort, this soup is perfect for busy weeknights, meal prep, or entertaining guests. The cheesy, crusty topping takes it over the top.

ingredients

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

• Yellow onions, thinly sliced
• Unsalted butter
• Olive oil
• Garlic, minced
• Brown sugar (optional, for enhanced caramelization)
• Beef broth (low sodium preferred)
• Worcestershire sauce
• Balsamic vinegar (optional, for depth)
• Fresh thyme (or dried thyme)
• Bay leaves
• Salt and black pepper
• French bread or baguette slices, toasted
• Gruyère cheese or Swiss cheese, shredded

directions

1. In a large skillet over medium heat, melt butter and olive oil. Add sliced onions and cook, stirring occasionally, for about 20–25 minutes until golden and caramelized. Add garlic and brown sugar (if using) in the last few minutes.
2. Transfer the caramelized onions to the crockpot.
3. Add beef broth, Worcestershire sauce, balsamic vinegar (if using), thyme, bay leaves, salt, and pepper. Stir to combine.
4. Cover and cook on low for 6–8 hours or on high for 3–4 hours.
5. Remove bay leaves and adjust seasoning as needed.
6. Ladle soup into oven-safe bowls, top each with a toasted slice of bread, and sprinkle generously with shredded cheese.
7. Place bowls under the broiler for 2–3 minutes, or until cheese is bubbly and golden.
8. Serve hot and enjoy.

Servings and timing

This recipe serves 6 and takes about 6–8 hours on low or 3–4 hours on high, plus 20–25 minutes prep time.

Variations

• Vegetarian version: Use vegetable broth and skip Worcestershire sauce (or use a vegetarian version).
• Cheese options: Substitute Gruyère with Swiss, mozzarella, or provolone if preferred.
• Bread swap: Use sourdough, rye, or any rustic loaf for the topping.
• Add wine: Deglaze onions with ½ cup dry white wine before transferring to the crockpot for added depth.

storage/reheating

Store leftover soup (without bread and cheese) in an airtight container in the refrigerator for up to 4 days or freeze for up to 3 months. Reheat on the stovetop over medium heat or in the microwave. Add fresh bread and cheese before broiling and serving again.

FAQs

Can I caramelize the onions directly in the crockpot?

While possible, stovetop caramelization gives better flavor and texture. It’s worth the extra step.

What onions work best for this soup?

Yellow onions are traditional, but you can mix in some sweet onions for added depth.

Can I make this soup ahead of time?

Yes, it actually tastes even better the next day as the flavors develop more.

Do I need oven-safe bowls?

Yes, for broiling the cheese topping. If not available, toast the bread with cheese separately and place on the soup when serving.

Is Gruyère necessary?

Gruyère melts beautifully and has a nutty flavor, but Swiss, mozzarella, or provolone also work.

How can I thicken the soup?

French onion soup is typically broth-based, but you can simmer it uncovered for a while to reduce and concentrate the flavor.

Can I use chicken broth instead of beef?

Beef broth is traditional for its rich flavor, but chicken broth can be used in a pinch for a lighter version.

What if I don’t have balsamic vinegar?

You can omit it or use a splash of red wine vinegar or dry sherry for similar acidity and depth.

Can I freeze this soup?

Yes, freeze the broth and onions without bread or cheese for up to 3 months. Thaw and reheat before serving.

What’s the best bread for topping?

A crusty French baguette or rustic sourdough holds up well to the broiler and soup.

Conclusion

Crockpot French Onion Soup brings all the rich, savory goodness of the classic version with far less effort. Letting the slow cooker handle the work makes this dish perfect for both everyday dinners and special occasions. Topped with golden, bubbly cheese and toasted bread, it’s a soul-warming favorite you’ll come back to again and again.

Print