Slow Cooker French Onion Soup
2 years ago

Slow Cooker French Onion Soup

Let your slow cooker do the work in this classic, comforting soup recipe from Twin Cities food blogger greens & chocolate.

While I already have a delicious recipe for French Onion Soup on my blog, it’s one that requires a lot of hands-on time. The onions are slowly cooked in the oven for over two hours and then the soup takes another hour to cook on the stovetop. That’s a lot of time hanging around the kitchen, and while it’s true that French Onion Soup takes some time to develop flavors (and that recipe is completely worth it), I wanted to come up with a method in the slow cooker that was less hands-on.

This recipe requires more time overall, but it’s far less work, as you let the slow cooker do it all for you. To begin with, you caramelize the onions in your slow cooker overnight. Did you know your slow cooker can do that for you?!

You simply put your onions, some butter and salt in the slow cooker and let it go all night long on low. When you wake up, your kitchen will not only smell lovely, but you’ll also have deep brown caramelized onions.

After the onions are caramelized, you add the remaining ingredients of the soup and let it cook all day. Easy, right?

To top it off, I think the bread and cheese is crucial for French onion soup. While I’ve used many recipes that simply put the bread and cheese on top and broil it, this recipe bakes it for 20 minutes and then broils it. This allows the bread to really meld into the soup – when I made it, there wasn’t one bit of the bread that didn’t soak up the delicious broth.

Can I just say this soup got me the slightest bit excited for chilly weather? I love a good hot day, but after having this French onion soup, I’m craving a chill in the air.

Slow Cooker French Onion Soup

6 servings
Preparation time (active): 15 minutes + 20 minutes in the oven to finish
Preparation time (passive): 8-10 hours to caramelize onions, then 6-8 hours to cook soup

3 pounds white onions, sliced
8 tablespoons unsalted butter
1 teaspoon salt
8 cups beef broth
1 tablespoon Worcestershire sauce
¼ cup white wine (or white cooking wine)
1 tablespoon red wine vinegar
4 sprigs thyme, plus additional thyme for topping
Loaf of Italian bread, cut into ¾-inch slices, for topping
2 cups shredded Gruyère cheese


  1. Place onions, butter and salt in large slow cooker. Cook on low for 8-10 hours. This works best if you do it overnight.
  2. In the morning add beef broth, Worcestershire, wine, red wine vinegar and thyme. Season with salt and pepper to taste. Cover and cook on low for another 6-8 hours.
  3. Heat oven to 350 F. Place ovenproof bowls onto baking sheet. Ladle soup into bowls. Top each bowl with 1-2 slices of bread and about ⅓ cup of shredded cheese.
  4. Bake for 20 minutes.
  5. Turn on broiler and broil until golden brown, keeping a very close eye on it.
  6. Garnish with additional thyme leaves and enjoy!