Slow Cooker French Onion Soup

slow cooker french onion soup

When I made this soup for the first time I made a big mistake. Since my hubby comes home every day for lunch we usually reserve soup for lunch time. Since this soup takes 6-8 hours to cook in the slow cooker, and I didn’t feel like getting up in the wee hours to get started on it, I decided to make it the day before. It was a great plan, until a couple hours in when my house started smelling fabulous and I knew I had to wait a whole entire day before I could eat a bowl of it. It was torturous. I was tempted to skip on my dinner plans and just have it for supper. But, my will power persevered and I spooned it away in a storage container and stashed it in the fridge to be heated up the next day. It was so worth the wait.

I’ve never made French Onion Soup before. Mostly because James isn’t a fan of onions so I thought it would be off the list. Especially after having not so great versions at restaurants. But then, I had a rich, flavourful version that got me craving another bowl and I decided it was time to try it at home.

This was every bit as good as I hoped it would be. Rich and flavourful, slightly sweet and oh so comforting. And, you know what, it even satisfied the picky onion eaters in the family. The kids, hubby and I gobbled it right up.

Normally you place the bread on top of the soup bowls and then broil it, but since I don’t have oven safe soup bowls we broiled the bread separately and placed it on top. It’s just as delicious and makes for any easy dipper for little people who may have a harder time getting their spoon to break up the bread. I’m a little wary of soggy bread but both me and James loved this and when the bread soaks up the delicious broth there is absolutely nothing to not like about it.

slow cooker french onion soup

Slow Cooker French Onion Soup
Recipe Type: Soup
Serves: 8
  • 1/4 cup unsalted butter
  • 4 medium sweet onions, halved and thinly sliced
  • 3 garlic cloves, minced
  • 2 tablespoons balsamic vinegar
  • 2 tablespoons brown sugar
  • 1/2 teaspoon salt
  • 3 tablespoons flour
  • 1 cup beer
  • 2 quarts low-sodium beef stock
  • 2 tablespoons chopped fresh thyme (or 1.5 teaspoons dried)
  • 1/2 teaspoon pepper
  • 1 baguette, sliced
  • Gruyere cheese, sliced or grated (harvarti is also good)
  1. Turn on your slow cooker and set to high. Add butter and let melt. Add onions, garlic, vinegar, brown sugar, and salt. Mix well. Cover and let cook for 1-1.5 hours, stirring every 15 minutes, until onions begin to caramelize and turn brown. Stir in flour, allow to cook for a couple minutes then stir in beer and beef stock a bit at a time, stirring well between each addition to avoid lumps. Stir in thyme and pepper. Cover and cook for 6-8 hours on low. Taste and season with additional salt, if desired.
  2. To serve: Top baguette slices with cheese and broil until cheese is bubbly and golden. Serve on top of soup. Alternately, if your soup bowls are broiler safe you can place the bread and cheese right on the soup and broil.

Adapted from How Sweet it Is. Originally from Tyler Florence.


  1. Becca @ Amuse Your Bouche says

    Love the idea of making this in the slow cooker! Will definitely be trying this one :)

  2. Roxanne says

    What kind of beer do you use . Sorry for the question I just never made onion soup ;)

    • says

      It doesn’t really matter. Since you won’t be drinking it straight up and it will be cooking for so long, it’s not necessary to use a certain brand. They will all impart the necessary flavour. :)

      • The Voice of Reason says

        I think it does matter…..darker beer can be a detriment in cooking…how ever using a “cheap lager” can make it taste terrible too….basically it’s trial and error when it comes to “which beer to use”…I would say….avoid lager…..and avoid dark ales….and go somewhere in-between and see what happens?

  3. Amanda says

    We don’t have beer in the house, but we do have a bottle of angry orchard cider… do you think this would taste good with that? Or should I go buy a bottle of beer?

  4. Michael says

    Awesome soup! My first attempt at French onion soup and it is soooo good! Eating a second helping now!

  5. Amanda says

    The directions were easy and the soup turned out SO GOOD! This was my first time making french onion soup; I used an ale beer. I paired my soup with a slice of french baguette and Applewood Smoked Gruyere cheese, DELICIOUS! ate the entire crock pot in one weekend (oops!). Making this again today, can’t wait for the house to smell yummy!

  6. Lisa R says

    wow, would have never know that beer was in onion soup, gotta try this one, I have all the ingredients except the unsalted butter, I have mozzarella, I think it’ll work with the butter I have.
    sibabe64 at ptd dot net

  7. Courtney Glantz says

    Alright – made this yesterday and we are SO in love! One tip if people want to cut down on time a bit – I did all the caramelizing on a saute pan on the stove, which only took 15 minutes or so – then I added to the slow cooker with the broth, beer, etc. I was short(er) on time due to the morning snow and this way worked great! 6 hours later we were eating the best french onion soup ever – thank you! I will be sharing this recipe soon!

  8. Stephanie says

    I made this soup last night and used an amber ale “Fat Tire” and also used seasoned croutons instead of the french bread and It was amazing! We both had a second bowl!

  9. Sharon says

    Love it. Better than any I bought before. Making my second pot today to use up the beer and excess onions.

  10. Noelle says

    Making this at the moment and boy does it smell good! I added a bit more flour for the density of it, and a tad more balsamic, we have mozzarella for the cheese! I’m excited, thank you for the post sweet gal! I cried enough tears to make a river while making this, haha.

  11. shuddec says

    Making this tonight, a vegetarian version for lunch and dinner tomorrow. I now have a small crock pot at work to heat soups in. Can’t wait