This Slow Cooker French Onion Soup is loaded with caramelized onions, a rich broth, and topped with crusty bread and melty cheese! It’s just like the classic version with a more hands-off approach for busy days.
If you want more cozy slow cooker soups for busy days, you’ll love this Creamy Chicken Noodle Soup Recipe, Chicken Pot Pie Soup, or Crockpot Zuppa Toscana!
Table of Contents
- Why we love this Crockpot French Onion Soup recipe:
- Crockpot French Onion Soup Ingredients:
- How to make French Onion Soup in the slow cooker:
- How do I store and reheat French Onion Soup?
- Can I freeze French Onion Soup?
- Make-ahead option:
- Serving suggestions:
- More slow cooker soup recipes you’ll love:
- Slow Cooker French Onion Soup Recipe
This Slow Cooker French Onion Soup has the same flavors as traditional French Onion Soup but is made in the slow cooker for a low-fuss version.
Any good French Onion Soup starts with caramelizing the onions for that iconic depth of flavor. After the caramelization process, the rest of the soup is a breeze!
The crowning glory is the crusty, cheesy bread on top that provides the perfect contrasting texture and creaminess.
Why we love this Crockpot French Onion Soup recipe:
- Low-effort: The slow cooker does all the heavy lifting for you in this recipe, minus the onions, for a cozy dinner you’ll want to come home to after a busy day!
- Rich flavors: Caramelizing the onions before adding them to the slow cooker develops rich flavors that only get better as they slowly cook for hours.
- Make-ahead friendly: You can prep this recipe ahead of time for a low-stress dinner!
Crockpot French Onion Soup Ingredients:
- Oil: Use any neutral oil like vegetable or canola to cook the onions.
- Yellow onions: These are a classic French Onion Soup ingredient that adds so much flavor!
- Salted butter: Adds richness and flavor.
- Brown sugar: Helps the onions caramelize and adds sweetness.
- Dried thyme: You can use fresh thyme if you have it on hand!
- Red chili flakes: Just a pinch for some warmth.
- Low sodium beef broth: I like to use low sodium broth to control the amount of saltiness in the soup.
- Dry white wine: Adds some zing and a depth of flavor to the soup! Sauvignon Blanc, Pinot Grigio, or an unoaked chardonnay are all great options. You can also use more broth if you want to skip the wine.
- Bay leaf: For a little extra flavor depth.
- French bread or baguette slices: You want to use sturdy, crusty bread that can hold up to the soup and cheese. I love using French bread or baguette slices!
- Shredded cheese: Gruyère, Mozzarella, and Swiss cheese are the best choices for creating that perfect gooey, golden topping! You can also use Parmesan cheese for a bit of sharpness.
How to make French Onion Soup in the slow cooker:
French Onion Soup is so much easier to make in the slow cooker! Don’t forget to check the recipe card for the full list of recipe instructions.
- Cook the onions and add butter, brown sugar, salt, thyme, pepper, and red chili flakes. Cook until caramelized.
- Transfer the onions to the slow cooker and add broth, wine, and bay leaf. Slow cooker until tender and flavorful.
- Toast the bread in the oven until golden brown and crispy, add the cheese to melt.
- Ladle into bowls and top with bread slices.
How do I store and reheat French Onion Soup?
Let the soup cool, then store it in an airtight container in the refrigerator for up to 3-4 days.
To reheat, warm it on the stovetop over low heat, adding a splash of broth if it’s too thick. You can also reheat it in the microwave if you’re in a pinch!
Top with cheese toast just before serving.
Can I freeze French Onion Soup?
Yes, you can freeze the soup without the bread and cheese. Store the cooled soup in a freezer-safe container for up to 3 months!
When ready to eat, thaw overnight in the fridge and reheat. Toast fresh bread and add cheese just before serving.
Make-ahead option:
You can prep this recipe ahead of time by adding all the ingredients into the slow cooker up until the point of cooking and refrigerate for up to 4 days.
Don’t forget to caramelize the onions before adding them to the slow cooker as this is where a lot of the flavor comes from!
Serving suggestions:
I love serving this soup with a side salad, Roasted Green Beans, or Air Fryer Broccoli for some greens!
And since you can never have too much bread, I always like to serve some crusty No Knead Artisan Bread or Mom’s Homemade Buns to dunk in the soup.
More slow cooker soup recipes you’ll love:
- Slow Cooker Cheeseburger Soup — big on flavor!
- Slow Cooker Chicken Gnocchi Soup — the ultimate comfort food.
- Slow Cooker Creamy Chicken Noodle Soup — a classic made easier!
- Slow Cooker Beef Barley Soup — a classic made easier.
Slow Cooker French Onion Soup
written by Ashley Fehr
Ingredients
- 1 tablespoon oil
- 4 large yellow onions
- ¼ cup salted butter
- 1 tablespoon brown sugar
- 1½ teaspoons salt
- ½ teaspoon dried thyme
- ¼ teaspoon pepper
- ⅛ teaspoon red chili flakes
- 5 cups low sodium beef broth
- ⅔ cup dry white wine (or sub additional broth)
- 1 bay leaf
- 4 thick slices French bread or 8 slices baguette
- 2 tablespoons salted butter
- 1 cup shredded cheese (Gruyere, Mozzarella, Gouda, Swiss, Parmesan, Asiago, etc. — a combination if possible)
Instructions
- Heat the oil in a large skillet over medium-high heat.
- Slice the onions thinly (I like to cut shorter slices — from a quarter onion rather than a half — so they fit more nicely on the soup) and add to the skillet.
- Cook and stir until softened and starting to brown, about 10 minutes.
- Add the butter, brown sugar, salt, thyme, pepper and red chili flakes. Cook and stir until beginning to caramelize, about 5 minutes.
- Place the onions in a 3-4 quart slow cooker and stir in the broth, white wine (or sub broth) and bay leaf. Cook on low for 6-8 hours.
- Just before serving, preheat the oven to 425℉. Lightly butter both sides of the bread slices, and place on a parchment lined baking sheet.
- Place in the oven and toast for 3-4 minutes, then flip and top each with cheese. I like to use 2-3 cheeses for the best flavor, but the kinds you use are very customizable. If adding hard cheeses, I recommend only a small sprinkling of those along with a good melting cheese.
- Bake for 3-4 minutes, until toasted and golden.
- Taste soup and adjust seasonings as desired. Ladle into four bowls and top with toasted bread slices. Serve.
Notes
- Onions: you can use a wide variety of onions in this recipe, or a combination. White and Vidalia onions also work well.
- Seasonings: you can add in a variety of fresh or dried herbs according to your tastes.
- White wine: if using wine, be sure to choose a dry and not a sweet wine. If not using wine, you can substitute for additional beef or chicken broth.
- Refrigerator: you can prep this recipe up to the point of slow cooking, then put the lid on and place it in the refrigerator up to 4 days before slow cooking and topping.
- Freezer: this recipe freezes very well without the toasted bread! Simply cook, cool and place in freezer-safe containers (the entire batch or individual servings), then thaw and heat before topping.
Nutrition Information
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