Create a comforting bowl of Slow Cooker French Onion Soup right in your crockpot! This recipe features a rich, buttery onion broth, perfectly paired with golden homemade croutons and melted cheese broiled to perfection on top.

It’s soup season (actually, every season is soup season for me). My family also enjoys slow cooker baked potato soup and slow cooker ham and bean soup. If you want a chicken version of this soup, try my Slow Cooker French Onion Chicken recipe.

Yes, you can make French Onion Soup in your crock pot!

Crockpot French Onion Soup brings restaurant-quality flavor right to your kitchen! Unlike traditional versions that can taste like plain beef broth and onions, my recipe is elevated with butter, balsamic vinegar, and a blend of spices for incredible depth. Plus, don’t miss my tips for perfect croutons to serve under the melty cheese.

If you love this soup, then try my Slow Cooker French Onion Dip, or my Slow Cooker French Onion Pot Roast.

What you need

• Onions – Use sweet onions (white or yellow, or red onions work too). These are often labeled Vidalia onions.
• Sugar – Optional; only use if you can’t find sweet yellow onions.
• Salted Butter – Used to caramelize the onions.
• Flour – Added to the butter and onions. This will add some body to the soup.
• Beef broth – Can use beef stock or chicken if desired. Vegetable broth is another option if you already have that on hand.
• Balsamic Vinegar – Adds flavor and a touch of tang.
• Worcestershire sauce – My secret ingredient for many slow cooker recipes.
• Seasonings – Salt, pepper, oregano, thyme, garlic, and a bay leaf.
• Toppings – Homemade Croutons (recipe below), Swiss cheese, and Parmesan cheese.
• (See the full recipe and instructions in the recipe card below the photos).

How to make:

How to caramelize the onions:

• Set a pan to medium-high heat. Add the butter. When the butter is melted, add the onions and sprinkle with salt and pepper.
• Cook the sliced onions until browned and caramelized; this can take 10 or more minutes. Stir often.
• I add the flour to the butter and onions and cook for two more minutes.

Make the soup in the slow cooker:

• Add the floured onions to the slow cooker. Add the beef broth, sugar (if using), garlic, thyme, oregano, Worcestershire sauce, and balsamic vinegar. Stir well. Add the bay leaf on top.
• Cook on HIGH for 4 hours or LOW for 8 hours.
• Remove bay leaf before serving. Now, you need to assemble the onions.

How to make homemade croutons:

• Preheat the oven to 500 degrees (broil).
• Cut a baguette into 1/4 inch slices. Place bread slices on a sheet pan.
• Using a pastry brush, brush olive oil onto the baguette slices.
• Place the sheet pan under the broiler. Cook for about 3-5 minutes or until browned and toasty.
• Cut a garlic clove tip off and rub each piece of cooked bread with it. This will give the bread garlic flavor.

What Can I Use If I Don’t Have Bread?

• Store-bought croutons – Yes! This works well. When I worked at Marie Callender’s, they used bagged croutons for their French Onion Soup.
• Garlic bread or French Bread – Cut a loaf of store-bought garlic bread or French bread into cubes. Broil until crisp and browned.
• Stove-top stuffing – You can add a sprinkle of stove top stuffing, it will soak up some of the soup and give you a base to put your cheese.

How to assemble French onion soup in bowls:

1. Fill an oven-safe bowl with the French Onion Soup broth. Place the bowl in a pie tin or on a baking sheet. (You can make more than one bowl at a time).
2. Add the homemade croutons (or store-bought) on top of the soup.
3. Place 1-2 Swiss cheese pieces (can use provolone or Gruyere) and sprinkle on Parmesan cheese.
4. Broil until the cheese is golden brown and is bubbly.

Recipe FAQs

More Slow Cooker Soup Recipes:

• Slow Cooker Stuffed Pepper Soup
• Slow Cooker Broccoli Cheese Soup
• Slow Cooker Corned Beef and Cabbage Soup
• Slow Cooker Turkey Chowder
• Slow Cooker Tomato Soup
• Slow Cooker Black Bean Soup
• Slow Cooker Chicken Noodle Soup