This gluten-free and healthy Slow Cooker French Onion Soup is comfort food at it’s finest. It’s made using simple ingredients you likely already have in your pantry, is largely hands-off cooking, is an economical meal and is so rich and flavorful. It can be eaten as is as a light soup, or more traditionally topped with melted cheese and either store-bought or homemade bread.

Slow Cooker French Onion Soup

French Onion Soup is such a classic comfort food, it’s hard not to love. If you’ve only eaten it at restaurants you might think it’s difficult to make because it’s SO rich and flavorful, but truly it isn’t that hard at all! And we’ve made it even easier by throwing the whole thing in the slow cooker for easy, hands-off cooking! This Slow Cooker French Onion Soup is a great example of taking really basic pantry items like onions, broth and a few other simple ingredients and turning it into something amazing by slow and low cooking. Recipes using pantry staples are a great to have in your back pocket on days when you don’t have time to run to the grocery store but still want to be able to cook up a great meal for your family.

What is French Onion Soup Made Of

Traditionally French onion soup is made by slowly caramelizing onions on the stove top, which can require lots of babysitting and stirring to make sure the onions don’t burn. The onions are then coated in flour and simmered for longer with broth. This Slow Cooker French Onion Soup recipe however takes all the amazing flavors of this bistro classic and tosses them all in the slow cooker to make while you are busy doing other things! The first step is to cook all the onions for about 6 hours, which doesn’t require any stirring. This step can have some wiggle room if you are about and about because it’s hard to burn onions in the slow cooker, so if you aren’t home during the end of the 6 hours of cook time, the onions will likely be fine for 2-3 hours after. Next you simmer the onions in the broth for the remainder 2 hours of cooking time. Classic French onion soup is topped with a large crouton-like piece of bread and cheese. We’ve given directions on how to do this, but truly you can leave this off and this soup is still really flavorful!

What is the best onion to use for French onion soup

This Slow Cooker French Onion Soup recipes uses two kinds of onions. Yellow onion are more sweet with a really bright flavor and red onions have more depth with a touch of bitterness. Together they make a really nuanced and flavorful french onion soup!

Can you cook French Onion Soup in the Instant Pot?

The short answer is: yes! We’ve included the directions for cooking this soup in the Instant Pot in the notes section of this recipe. However we have to say that it is a little bit more hands on cooking than the slow cooker version.

If you like this slow cooker SOUP recipe, try these other favorites:

• Slow Cooker Chicken Soup
• Slow Cooker Sweet Potato Chili
• Slow Cooker Lasagna Soup
• Slow Cooker White Chicken Chili
• Slow Cooker Short Rib Stew

Want to try other crock pot comfort food favorites? Try these:

• Slow Cooker Apple Butter
• Slow Cooker Baked Potato Bar
• Slow Cooker Asian Beef Bowls

Watch the video:

Slow Cooker French Onion Soup

Print shopping list

Prep Time 00:15 Cook Time 08:30 Total Time 08:45 Serves 4-6

0.0 rating

Ingredients

• 3 tablespoons butter
• 1 tablespoon extra-virgin olive oil or avocado oil
• 4 white onions, sliced
• 2 red onions, sliced
• 1 tablespoon coconut sugar
• 3 cloves of garlic, minced
• 1 teaspoon salt, more to taste
• 1 teaspoon black pepper, more to taste
• 1/4 cup balsamic vinegar
• 2 teaspoons dried thyme or 2 fresh thyme sprigs
• 2 bay leaves
• 7 cups beef broth
• 1/2 teaspoon fish sauce
• 1 tablespoon arrowroot flour
• Optional: red pepper flakes, for serving
• Options: 1/4 cup shredded Gruyere cheese
• Optional: 1/4 cup shredded mozzarella cheese
• Optional: 1 batch bread (see recipe here or here for nut-free)

Directions

1. Place butter and oil in the bottom of your slow cooker insert.
2. Add in sliced onions, coconut sugar, garlic, balsamic vinegar, half the salt and pepper, thyme and bay leaves. Toss to coat and cook on low for 6 hours.
3. After 6 hours, add in beef broth, fish sauce, arrowroot flour, and the remaining salt and pepper.
4. Let cook for the remaining 2 hours. Remove bay leaves and thyme sprigs if using fresh thyme. Taste and add salt and pepper as desired.
5. Heat the oven to 350°F. Divide the soup between oven-safe bowls. Top each with a slice (or two) of toasted bread and sprinkle cheese in a thick layer over the bread and up to the edge of the bowl. Bake for 20 to 30 minutes until cheese is bubbling. Broil on high for 1 minute.

Recipe Notes

1. To make in the Instant Pot:
   1. Press the saute function on the Instant Pot.  When hot place butter and oil in the pot along with the onions. Cook for 5 minutes, stirring once. Add in coconut sugar, garlic, balsamic vinegar, salt and pepper, thyme and bay leaves and cook on high pressure for 20 minutes. Once finished use the quick release function
   2. Press cancel and remove the lid. If there is a lot of liquid in the bottom of the pot, press saute and cook until it has almost evaporated and the onions are a nice brown color and very jammy. 
   3. Add the arrowroot and stir until it has disappeared. Add in 4 cups of beef broth (this is different than the directions for the slow cooker) and fish sauce and close the lid and set to sealing. Finish cooking on manual high pressure, for 5 minutes. Use the quick release function. Season to taste. If topping the soup with bread and cheese follow the directions up above from step 5.

Loading nutrition data...

There may be affiliate links in this post! By clicking on them, or purchasing recommended items I may receive a small compensation, at no cost to you! However, I only recommend products I absolutely love and use in my own home! Thank you for supporting Lexi's Clean Kitchen when you shop! See my privacy policy for more information about this, the information we save, and more!

Related Posts:

Classic Chicken Soup (Slow Cooker & Instant Pot) Crock-Pot Stuffed Pepper Soup Slow-Cooker Beef Stew Slow Cooker Thai Curry Chicken [VIDEO]