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Crockpot French Onion Soup has every bit of depth, flavor, and bubbly, broiled cheese as the original version, with a little less hands-on cooking! Let your slow cooker caramelize the onions to perfection, then add a flavorful broth and broil with toasty slices of bread and Gruyere for that signature finishing touch.

Crockpot French onion soup in two bowls

Why You’ll Love This Slow Cooker French Onion Soup Recipe

  • Caramelized Onions Made Easy. If you’ve ever struggled to get perfectly jammy caramelized onions on the stovetop, or don’t have the patience, you’ll love the hands-free slow cooker method (check out my Instant Pot French Onion Soup too). Simply add thinly sliced onions and let them cook low and slow for several hours until they become soft and sweet.
  • Deep, Rich Flavors. Some homemade French onion soup recipes taste like onions and broth. Sad! This crockpot French onion soup won’t let you down, with a rich broth flavored with thyme, white wine, and irresistible slow-cooked onions. ( and French Onion Soup Recipe won’t disappoint either!)
  • The Bread! The Cheese! The caramelized onions are fabulous, but let’s be real: we wouldn’t eat French onion soup if it wasn’t for that crusty bread and melty cheese on top.
  • The Coziest Dinner. Slow cooker dinners like Crockpot Chicken and Potatoes have cozy vibes in spades, as do warm bowls of soup (ahem: Broccoli Cheddar Soup). This crockpot French onion soup is the perfect meal for a chilly night in. Plus, your house will smell fantastic as it simmers away all day!
Spoonful of crockpot French onion soup lifted from bowl

How to Make Crockpot French Onion Soup

The Ingredients

  • Unsalted Butter. Although any butter will do, this is a great recipe to spring for the fancy European butter. (Oh la la!) 
  • Yellow Onions. Standard yellow onions are the best choice for this crockpot French onion soup. Or you can use a mix of onions for a signature flavor of your own.
  • Garlic. Although onions are the star of the show, garlic is a key supporting player!
  • Fresh Thyme. While fresh is best, you can use dried if you prefer.
  • Kosher Salt and Black Pepper. I love adding freshly cracked black pepper over the top of the cheese before broiling for some extra flavor.
  • Low-Sodium Beef Broth. Use a high-quality broth (homemade if you have it!) for the best results.
  • Dry White Wine. Such as Sauvignon Blanc. While you can just add extra broth in place of the wine, it really adds a lot of complexity and depth.
  • French Bread. French onion soup is a fabulous way to put stale bread to use!
  • Olive Oil. For toasting the bread.
  • Gruyere Cheese. Swiss cheese or Emmental cheese would both be good substitutes if you’re not a fan of Gruyere.

The Directions

Seasoned onions and thyme in crockpot
  1. Season the Onions. Combine with the butter, herbs, and spices in the slow cooker.
Caramelized onions in bottom of crockpot
  1. Caramelize. Cook on high for 5 to 7 hours, stirring occasionally, until the onions caramelize.
Pouring broth into crockpot for French onion soup
  1. Add the Liquid. Stir in the broth and wine. 
French onion soup in crockpot
  1. Cover and Cook a Little Longer. 30 more minutes.
Slices of bread floating in bowls of crockpot French onion soup
  1. Toast the Bread. Then drop them into the bowls of soup.
Slow cooker French onion soup topped with shredded cheese
  1. Broil the Tops. Add the cheese and broil until it’s browned, melted, and bubbly. ENJOY!
Two crocks of slow cooker French onion soup on sheet pan

Recipe Variations

  • Vegetarian Slow Cooker French Onion Soup. Use vegetable broth or mushroom broth in place of the beef broth to make this crockpot French onion soup vegetarian. Mushroom broth will give it more depth and richness, so I recommend using that if you can.
  • Crockpot French Onion Soup With White Beans. While the beauty of French onion soup lies in its simplicity, I will say that I’ve added a can of drained and rinsed white beans to the pot during the last 30 minutes (when adding the broth). It’s a great way to add some extra protein!
  • Crockpot French Onion Soup With Brandy. Not only can you make this soup with brandy, you can also try it with sherry or a dry red wine. Switching up the alcohol will give the soup a slightly different flavor.

Meal Prep Tips

You can slice the onions a day or two in advance and store them in an airtight container in the refrigerator. The cheese can also be grated in advance—it will keep up to two days.

What to Serve with Crockpot French Onion Soup

Recipe Tips and Tricks

  • Slice the Onions Thinly and Uniformly. It’s always a bummer to get a thick slice of onion in your soup, so be sure to slice them as thinly and uniformly as possible. A mandoline slicer can help with this task.
  • Don’t Use the Cheapest Wine. But don’t use the most expensive either! My rule of thumb for cooking is choosing a wine about two notches above the cheapest. You’re not going to notice all the nuances of a pricy wine when you’re using it to make soup, but you will notice a flat-out bad wine.
  • Shred Your Own Cheese. Trader Joe’s does sell a nice shredded Gruyere for when you’re in a time-crunch, but if at all possible, pick up a block of cheese and shred it yourself instead. It will be gooey-er and meltier and you won’t regret it.
Spoonful of slow cooker French onion soup being lifted from bowl

Crockpot French Onion Soup

5 from 13 votes
Crockpot French onion soup with caramelized onions, rich broth, toasted bread and melted cheese just like traditional French onion soup, done easy and hands free in the slow cooker!

Prep: 25 minutes
Cook: 7 hours 30 minutes
Total: 8 hours

Servings: 5 servings

Ingredients
  

  • 2 tablespoons unsalted butter melted
  • 3 pounds yellow onions thinly sliced (6 medium onions)
  • 4 garlic cloves minced (about 4 teaspoons)
  • 1 tablespoon fresh thyme leaves or 1 teaspoon dried thyme
  • 1 1/2 teaspoons kosher salt plus additional to taste
  • 1/4 teaspoon ground black pepper
  • 4 cups low-sodium beef broth (1 quart)
  • 1/2 cup dry white wine such as Sauvignon Blanc
  • 8-12 slices French bread 1/4-inch thick
  • 3 tablespoons olive oil
  • 1/2 cup shredded Gruyere cheese

Instructions
 

  • In a 6-quart slow cooker, combine the butter, onions, garlic, thyme, salt and pepper. Cover and cook on high for 5 to 7 hours, stirring occasionally, until the onions are caramelized.
  • Stir in the broth and wine. Cover and cook on high for 30 additional minutes.
  • Meanwhile, place a rack in the upper third position of the oven (about 6 inches from the top) and preheat the broiler. Arrange the bread slices on a baking sheet. Brush both sides with the oil and place under the broiler for 2 to 3 minutes per side, keeping a close eye on them and rotating the pan to avoid burning. Remove from the oven.
  • When the soup is done, divide it between 4 oven-safe bowls or ramekins. Place 2 or 3 baguette slices on top of each ramekin and sprinkle about 2 tablespoons of cheese on top of each.
  • Place the bowls on a baking sheet and broil for about 2 minutes, until browned and bubbling, keeping a close eye on them under the broiler. Sprinkle with a pinch of salt and pepper and serve.

Notes

  • SUBSTITUTION NOTES: I don’t really recommend substitutions, but in a pinch, you could use chicken or vegetable broth (veggie broth would be fine for vegetarians). Swiss cheese or Emmental would work (but gruyere is the best!)
  • TO STORE: Refrigerate leftover soup (without the toppings) in an airtight storage container for up to 4 days. Store bread separately in an airtight storage container at room temperature.
  • TO REHEAT: Rewarm leftovers in a pot on the stovetop over medium-low heat or in the microwave. Then, top with the toasted bread and cheese and broil as directed in the recipe.
  • TO FREEZE: Freeze soup in an airtight, freezer-safe storage container for up to 6 months. Let thaw overnight in the refrigerator before reheating.

Nutrition

Serving: 1(of 4)Calories: 593kcalCarbohydrates: 80gProtein: 21gFat: 20gSaturated Fat: 7gPolyunsaturated Fat: 2gMonounsaturated Fat: 9gTrans Fat: 0.2gCholesterol: 27mgSodium: 1774mgPotassium: 950mgFiber: 7gSugar: 17gVitamin A: 338IUVitamin C: 23mgCalcium: 264mgIron: 5mg

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Erin Clarke

Hi, I'm Erin Clarke, and I'm fearlessly dedicated to making healthy food that's affordable, easy-to-make, and best of all DELISH. I'm the author and recipe developer here at wellplated.com and of The Well Plated Cookbook. I adore both sweets and veggies, and I am on a mission to save you time and dishes. WELCOME!

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  1. Thank you so much for this recipe. It was absolutely amazing. I’ve always been too intimidated to make this soup for myself. It brought me back to a little French restaurant my mom used to take me to when I was younger.5 stars

  2. My hubby LOVES french onion soup so we tried this recipe together. I have to say it is the best soup recipe I’ve tried from this site. The first time I made this we didn’t have any wine in the house so I deglazed the onion pan with bourbon and we really liked it. Also add a few squirts of soy sauce at the end5 stars

  3. I wish I could give this recipe more than 5 stars. It’s that easy and incredibly delicious. There are so many French onion soup recipes out there that I didn’t know which one to choose. But I’ll tell ya, I’m glad I chose this one! To me, it tasted like a bowl that you’d order at a restaurant. I was so happy with this recipe that I’m actually sautéing the onions now to make it for my family tomorrow!5 stars

  4. I have made both the stovetop version and this crockpot version! Both delicious! The ease of tossing the onions in the slow cooker and not worrying about dinner later was well worth it.5 stars