Slow-Cooker French Onion Soup


Thanks to your slow-cooker, this soup is filled with flavor without all the work.

Active Time:
15 mins
Total Time:
6 hrs 50 mins
6 serves

The French may have first invented French onion soup, but Southerners are revolutionizing this classic dish with the help of one of our favorite kitchen gadgets: The slow-cooker. We'll take any chance we can get to break out our slow cookers, but after testing this recipe, we can confirm that this classic soup is even tastier (and easier than ever!) when prepared in the slow cooker. In a soup that is simple, leaning on only a few ingredients to deliver maximum flavor, a slow-cooking method really allows time to draw out all the sweetness and richness that tender caramelized onions bring to the table. In this recipe for Slow-Cooker French Onion Soup, deep, rich caramelized onions get a little zing from sherry vinegar, which is then topped with bread and gooey cheese—really, what more could we ask for? Caramelized onions are notoriously fussy and time-consuming, but this genius method seriously cuts down the hands-on work (read: no babysitting your onions on the stove). Save at least 30 minutes at the stove by using the slow cooker to make sweet, tender onions that require (almost) no stirring. Start your onions in the morning and enjoy the rich smell of caramelizing onions all day without all the fuss. This soup makes a lovely starter, paired with another French classic like moules frites or cast-iron seared steak, but it's also substantial enough to act as the main event.


  • 2 pounds Vidalia onions, thinly sliced (about 8 cups sliced)

  • ¼ cup unsalted butter, melted

  • 1 ½ teaspoons granulated sugar

  • 1 ½ teaspoons kosher salt

  • ½ teaspoon black pepper, plus more for garnish

  • 6 thyme sprigs, tied with kitchen twine 

  • 1 dried bay leaf

  • 5 cups lower-sodium beef broth 

  • 1 tablespoon sherry vinegar

  • 12 (½-inch-thick) baguette slices 

  • 6 ounces Gruyère cheese, shredded (about 1 ½ cups)

  • Fresh thyme leaves 


  1. Stir together onions, melted butter, sugar, salt, and pepper in a 6-quart slow cooker until onions are fully coated. Place thyme and bay leaf on onion mixture. Cover and cook on HIGH, stirring once halfway through, until onions are deep golden brown and caramelized, 6 to 7 hours.

  2. Remove and discard thyme and bay leaf. Stir in broth and vinegar. Cover and cook on HIGH until thoroughly heated, about 30 minutes.

  3. Preheat oven to broil, with oven rack about 6 inches from heat. Spoon soup into 6 ovenproof ramekins; place on a large rimmed baking sheet. Top each ramekin with 2 baguette slices; divide cheese evenly among ramekins (about ¼ cup each). Broil until cheese is melted and golden brown, about 3 minutes. Sprinkle with fresh thyme leaves and black pepper. Serve immediately.

    Slow-Cooker French Onion Soup
    Victor Protasio; Food Styling: Rishon Hanners; Prop Styling: Audrey Davis
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