This Slow Cooker Beefy French Onion Soup is the best version of French Onion soup ever!

Slow Cooker Beefy French Onion Soup

  • Author: Dan
  • Prep Time: 45 minutes
  • Cook Time: 8 hours 45 minutes
  • Total Time: 9 hours 30 minutes
  • Yield: 8 1x

This slow cooker french onion soup is so rich and hearty, the homemade beef stock is so worth making!



For the Stock

  • 3 lbs. short ribs, seasoned with salt and pepper
  • 1 tablespoon kosher salt
  • 2 sprigs fresh tarragon
  • 1 teaspoon peppercorns
  • 1 teaspoon dried parsley
  • 1 teaspoon dried thyme
  • 5 carrots, peeled and cut into large pieces
  • 2 medium onions, peeled and quartered
  • 5 celery stalks, cut into large pieces
  • 10 cups water

For the Caramelized Onions

  • 6 medium to large onions, peeled, cut in half and sliced
  • 2 tablespoon butter plus 1 tablespoon olive oil
  • 1 teaspoon salt
  • 1/2 teaspoon dried thyme
  • 1/4 cup marsala wine

Soup Topping

  • 4 cups gruyere cheese, shredded
  • 1 french baguette, sliced and lightly toasted (you’ll need 2 pieces for each bowl of soup)


  1. Preheat the oven to 425 degrees. Place the seasoned ribs on a sheet pan, drizzle with olive oil and roast for 45 minutes, turning once half way through cooking.
  2. Once the ribs are roasted, place them into a slow cooker along with the rest of the ingredients for the stock and set on low heat for 8 hours.
  3. Remove the bones from the stock and place into a bowl to cool.
  4. Shred the meat from the bones, discarding any fat and set aside.
  5. Carefully pour the stock through a strainer into a large pot. You can throw the out the vegetables used in the stock.
  6. Once the stock has cooled, cover and place in the refrigerator overnight.
  7. When you’re ready to make the soup, remove the layer of fat from the stock and discard.
  8. Place the pot over medium heat (uncovered so the stock reduces) and bring to a boil. Turn down and let simmer while you make the onions (about 30 minutes).
  9. Add the butter and olive oil to a large skillet along with the sliced onions over medium-low heat.
  10. Add the salt and thyme and stir to combine.
  11. Let the onions cook, stirring often, for at least 30 minutes until the onions are brown and caramelized. The time it takes to caramelize will depend on the size of the skillet you are using, but they should be completely soft and brown in color when they are done. After the 30 minutes are up and the onions are caramelized, add the marsala wine and cook another 5 minutes.
  12. Now add the onions to the simmering stock along with the beef you removed from the bones.
  13. Stir and let simmer for another 15 minutes, then test for seasonings.
  14. Preheat the broiler.
  15. Fill each oven proof bowl with onion soup, then top with one or two pieces of toasted bread.
  16. Cover the bowl with cheese then repeat with the remaining soup bowls.
  17. Place the bowls on a sheet pan under the broiler for 3-4 minutes until the cheese melts and starts to get toasty on top.
  18. Remove from the oven and serve piping hot!

Recipe Notes

You’ll need oven safe bowls or soup crocks for this recipe!

  • Category: soup
  • Method: slow cooker/stove top
  • Cuisine: American

Keywords: french onion soup, onion soup, soup recipe, slow cooker soup, slow cooker onion soup, beef recipes, short ribs, gruyere cheese