Slow Cooker French Onion Soup

Make Slow Cooker French Onion Soup in your slow cooker. It has a rich buttery onion broth that is great with homemade croutons and cheese broiled on top.

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

Crockpot French Onion Soup is just as good as any fancy restaurant. My version doesn’t just taste like beef broth and onions. I add butter, balsamic vinegar, and spices, so the soup has a depth of flavor and see my tips for making the croutons that go under the cheese when serving.

Recipe Ingredients

• Onions – Use sweet yellow onions (white or yellow, or red onions work too)
• 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 chicken if desired.
• Balsamic Vinegar – Adds flavor and touch of tang.
• Worcestershire sauce – My secret ingredient.
• Seasonings – Salt, pepper, oregano, thyme, garlic, and a bay leaf.
• Toppings – Homemade Croutons (recipe below), swiss cheese, and parmesan cheese.

How to carmelize 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 2 more minutes.

• Add remaining ingredients.
• Stir.

How long do I cook?

• Place the lid on the slow cooker.
• Cook on HIGH for 4 hours or on low for 8 hours.

How to make homemade croutons:

• Preheat the oven to 500 degrees (broil).
• Cut a baguette into 1/4 inch slices. Place slices on a sheet pan.
• Using a pastry brush, brush olive oil onto the 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 – This buttery onion soup is amazing topped with a bit of stuffing mix under the cheese.

How to serve this recipe:

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.

What is the best cheese for this recipe?

• Swiss Cheese or Baby Swiss
• Gruyere Cheese
• Mozzarella Cheese
• Parmesan cheese – in addition to the above cheeses.

Can I freeze this soup?

• Yes, you can freeze the leftover soup (without the croutons and cheese).
• Place the cooled soup into freezer ziplock bags or freezer containtes.
• Freezer for up to 3 months.
• Thaw in fridge for 24 hours before needing.
• Reheat on the stove-top or microwave.

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Try one of these soups next:

• 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