Slow Cooker French Onion Soup Recipe -
Slow Cooker French Onion Soup Recipe
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Slow Cooker French Onion Soup
A cheesy French onion soup with a comforting beefy broth. See more
  • READY IN 5+ hrs

Slow Cooker French Onion Soup

Recipe by  

"This is a ridiculously easy soup, especially since it cooks in a slow cooker! When it's been simmering all day, you come home to an amazing aroma and a fabulous meal for a cold winter day."

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Ingredients Edit and Save

Original recipe makes 8 servings Change Servings
  • PREP

    30 mins
  • COOK

    4 hrs 35 mins

    5 hrs 5 mins


  1. Heat butter in a large, heavy pot over medium-high heat; cook and stir onions until they become translucent, about 10 minutes. Sprinkle onions with sugar; reduce heat to medium. Cook, stirring constantly, until onions are soft and browned, at least 30 minutes. Stir in garlic and cook until fragrant, about 1 minute.
  2. Stir sherry into onion mixture and scrape bottom of pot to dissolve small bits of browned food from the pot. Transfer onions into a slow cooker and pour in beef broth. Season to taste with sea salt; stir in thyme and bay leaf. Cover cooker, set on High, and cook 4 to 6 hours. If desired, set on Low and cook 8 to 10 hours.
  3. About 10 minutes before serving, set oven rack about 8 inches from the heat source and preheat the oven's broiler. Arrange bread slices on a baking sheet.
  4. Broil bread slices until toasted, 1 to 2 minutes per side.
  5. Combine Gruyere, Emmental, Parmesan, and mozzarella cheeses in a bowl, tossing lightly. Fill oven-safe soup crocks 3/4 full of onion soup and float a bread slice in each bowl. Top with about 2 tablespoons of cheese mixture per serving.
  6. Place filled bowls onto a baking sheet and broil until cheese topping is lightly browned and bubbling, about 2 minutes.
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  • Cook's Note:
  • You do not HAVE to caramelize the onions, you CAN simply melt the butter in your crock, add the onions to coat them and then add all the ingredients and cook. HOWEVER, caramelizing the onions makes for a much much better soup!!!! :) If you like, simply put all the options out on the table and let people make their own! This seems to be the popular method when I have a craft night. People can make their own decisions about what they want in or on their soup!
  • Easy Cleanup
  • Try using a liner in your slow cooker for easier cleanup.

Reviews More Reviews

Most Helpful Positive Review
Sep 26, 2012

Excellent! I followed this recipe to the letter (with the exception of substituting the Gruyere and Emmental with provolone and Swiss) and the soup was to weep for. The smell drove us mad all day long: it was hard to wait 8 hrs! Thanks for the recipe!

Most Helpful Critical Review
Jun 28, 2014

Even more ridiculously easy: Caramelize the onions in the, lightly-oiled, crock pot (no butter, sugar or sherry needed, just time), add 4-6C beef stock (what's the point of low-sodium if you're going to add salt?), and forget the grated four-cheeses (use the traditional slice of Gruyere, Emmental or, if all else fails, generic Swiss). For individual servings, dissolve a beef bouillon cube in 6oz of boiling water, add 4-6oz caramelized onions, heat in microwave, add toasted bread and a slice of cheese and finish under the broiler.

Dec 29, 2012

This is a great recipe. I couldn't find Emmental so I subbed in Swiss. If you put the bread right in the soup it kind of soaks it up and turns soggy so you can coop that right up with your spoon along with the soup - or, if you don't like soggy bread you can not do that. The bread is definitely key, though.

Nov 06, 2014

I give this recipe 4 starts simply due to the prep work this particular one entails. The soup tasted amazing! However, for ease of cooking, here are my tweaks: First, I sliced the onions, and tossed them in the butter which I melted, and placed them in the crock pot on low on their own to caramelize over night, 10-12 hours. I used salted butter, so I omitted the salt. I also omitted the sugar since they were caramelizing this way. SUPER EASY. The next morning, when the onions were good to go, I threw in the other cooking ingredients to cook for the day. I had no cooking sherry, so I used a 1/2 cup of dry red wine my husband opened the night before. I am a firm believer that if you don't drink it you shouldn't cook with it. And I had 2 quarts of beef stock, so I used that all up. No sense wasting a cup. When it came to the cheese, we used what we like, so that is personal taste not tweaking. I did find, however, that I needed to add a bit of salt and pepper to taste at the end just before serving, so make sure you taste it to ensure it is to your liking. But allowing the onions to cook and caramelize themselves cut the prep work down to the bare minimum of slicing the onions, measuring the ingredients, and getting the bread and cheese ready at the end. About 20 minutes total. You just need to start it the day before, which was worth it to me if it meant not standing over a stove for an hour. Family loved it, warms well for leftovers, which wasn't too much. Will make again!

Nov 05, 2012

Hi - very very good and easy.

Nov 01, 2013

This is one of the better slow-cooker recipes I've tried. Do take the time to carmalize the onions - the fond makes a lot of difference. Whatever else you do, please do not use 'cooking' sherry, which isn't really sherry and tastes mainly like sour salt water. Use real cocktail (dry) sherry if you have it. If not, a little bourbon, red wine, or Mediera will do. And try to use the cheezes specified, but it you must substitute, regular Deli-style swiss and/or Provolone are better than Mozzerella, which is too bland and milky for the richness of the dish. Finally, I found that slow-baking the bread slices to dry them works better than toasting because the toasted bread is softer and will dissolve in the hot liquid too quickly.

Dec 08, 2012

WOW! I carmelized my onions early this morning. (took about an hour). I wouldn't skip this step - IT IS what makes the soup. You just can't duplicate that flavor! Also do NOT skip the sherry! I used Swanson beef stock, fresh thyme and a dried bay leaf. It is in the crock pot now and will be ready for when we come back from two junior high basketball games around 7 pm. Having it with hamburgers for dinner tonight. It is going to take ALL OF ME not to go in the kitchen to ladle a bowl in secret! WISH I had oven proof crocks, that way I could broil the cheese on top of the soup.....but we will improvise and it will still be great! GREAT RECIPE!

Dec 21, 2013

This is delicious but since you already spent 40 minutes cooking the onions on the stove and they are already nice and soft, why not just leave it on the stove and add the broth to that pot and simmer it for another hour or so? Transferring it to the slow cooker seems like an unnecessary step and just creates extra stuff to wash. This seems to be one of those recipes where using the slow cooker really doesn't simplify anything.


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  • Calories
  • 250 kcal
  • 12%
  • Carbohydrates
  • 17.5 g
  • 6%
  • Cholesterol
  • 38 mg
  • 13%
  • Fat
  • 14.7 g
  • 23%
  • Fiber
  • 1.5 g
  • 6%
  • Protein
  • 11 g
  • 22%
  • Sodium
  • 596 mg
  • 24%

* Percent Daily Values are based on a 2,000 calorie diet.

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