Classic French Onion Soup features a buttery beef broth loaded with caramelized onions. Cooked all day in your crock pot, then topped with crusty bread and melted cheese.
Let your crock pot to all the work for you.
Seasoning—thyme, salt, pepper
Serving—cheese (gruyere, provolone, or Swiss) and crusty bread
Featured comment from Judith:
"Will definitely be making again! It tastes just like the French onion soup from our favorite restaurant!! Thanks for a great recipe!"
This elegant comfort food is better than most restaurants, and you made it for pennies at home. Perfect for a small crock pot or double to make the family size.
French Onion Soup is more than a beef broth with some onions. You need to get the caramelization going well, and that takes time. We let the slow cooker do the work for you.
👨🍳How to Make French Onion Soup in a Crock Pot
Start with simple ingredients. The butter may be with or without salt.
Chop 1 ½ pounds of onions, about 3 medium size onions. Some people will want rings or petals—add to a 2 ½ quart or larger crock pot. 4 quarts or a larger crock pot are needed if doubling the recipe. Triple needs larger than 6 quarts.
Add 1 teaspoon of coarse salt, 2 tablespoons of butter, ½ teaspoon of black pepper, 1 ½ teaspoon Worcestershire sauce, and ½ teaspoon of thyme. Then, stir them together. The butter can go in unmelted, but you must stir in 1 hour or melt it in the microwave.
Cook on high for 9-10 hours with lid on until nicely darker brown. Be warned that some crock pots may run hot, and please watch for the endpoint of "softened and deep golden brown" for the onions being done, and don't go by time alone. Then add 4 cups of beef broth and cook on high for at least one hour.
Preheat the broiler to high. Arrange ramekin or oven-safe bowls on a cookie sheet. Ladle hot soup into the bowls and float toasted crusty bread on the soup.
Cover each bowl with the cheese of your choice.
Broil until cheese is bubbly and golden, 2-4 minutes.
For more details, keep reading. See the Recipe Card below for complete instructions and to print.
Note on ingredient quality: With many other recipes, you can use cheaper generic ingredients and get away with it. But with so few ingredients, quality matters here. So, only use ingredients you trust.
- Onions—Regular yellow or white onions are the best choices, but some red onions can be mixed in. Some prefer sweet onions like Vidalias, Mauis, and Walla Wallas to add sweetness.
- Beef Broth—Very few commercial beef broths or stocks are above adequate, and many are just bad. I suggest Swanson®️ broth or stock or use one you know. You can also do homemade stock or broth. Vegetable broth can be used.
- Seasoning—The seasoning is limited to some dry or fresh thyme with salt and pepper. One to two cloves of garlic can be added with the onions.
- Worcestershire sauce—will make the "beef" flavor pop and add more flavor. It can be used in many cooking applications to boost that beef test, especially beef broth. I'm using Lee and Perrins Worcestershire Sauce, which I trust, but I suspect there are other good choices.
- Cheese—gruyere, provolone, or Swiss cheese are preferred. But even mozzarella cheese will work.
- Crusty bread or croutons—toast a buttered slice of French bread on a baking sheet in the oven. Large croutons can also be used.
How to caramelize onions in a crock pot
Caramelization is the browning of sugar through the oxidation of those sugars. It results in a deep nutty flavor and brown color when correctly done. Just what we need for a great soup
Many techniques require multiple rounds of caramelization on the stovetop, which will keep you working all day at the stove. But you can do it in a crock pot. I'm lazy. I pick number two.
Start by loading a slow cooker with some chopped-up onions. Cook with butter, salt, pepper, and thyme. Add a little Worcestershire sauce to deepen the flavor. Cook on high for 9-10 hours, but this may be a few hours less or more, depending on your crock pot.
Related recipes you will love
Let's keep that crock pot out and try other great soup recipes. Start with Ham Bone and Bean Soup and then move on to Crock Pot Broccoli Cheese Soup, Crock Pot French Onion Soup, or Crock Pot Cheeseburger Soup.
♨️About the crock pot
This recipe fits well in a small crock pot of 2 quarts minimum. Double recipes (what I suggest making) need 4 quarts or bigger.
The volume of this recipe is about 6 cups. Slow cookers should not be overfilled, which means more than 75% full. Most feel that bigger is acceptable but may cook a bit faster.
Troubleshooting crock pot temperature
Several readers have had trouble with 9 hours on high "burning." Whether they are interpreting deep caramelization for burning or they are really burnt, I can't say, but let's talk about crock pots and their temperatures.
On a crock pot, the maximum temperature on both low and high should be 212° range, but it will take different times to get there. That is all controlled by a thermostat that has improved over the years.
Some crock pots (especially older ones) can run much hotter, which may be the issue. Also, even newer crock pots can have a malfunctioning thermostat. So be advised that some crock pots may run hotter, so watch for "softened and deep golden brown" as the endpoint for the onions being done.
If you are using a full-size crock pot for this smaller recipe, you have less material to heat, and it may cook a bit faster.
I'm firm with my 9-10 hours on high, which is consistent with other similar recipes, and less than American Test Kitchen (subscription required), which is 10-12 hours on high.
How to serve French Onion Soup
Serve as a main dish, an appetizer, or a side dish. Traditionally served in a small bowl topped with browned cheese supported with croutons or a slice of crusty bread.
For the cheese, we like provolone, but some prefer gruyere or Swiss cheese. I like to use slices of cheese, but shredded cheese works fine. Again, quality matters.
For the bread, I chose a nice crusty French baguette if available. Other crusty breads or large croutons are used to float cheese, also. You can skip it, but it is traditional and helps keep the cheese on top.
How to store leftovers
Store leftovers sealed airtight and refrigerated for 4 days or frozen for 4 months.
Reheat, after thawing overnight in the refrigerator if frozen, on the stovetop or in the microwave.
Wine is not required for onion soup. It has traditionally been used to de-glaze the pan after caramelizing the onions—not needed with a crock pot. But the wine also added flavor to the soup.
Never cook with wine you don't like. While I can enjoy food cooked with wine, it is not a taste I need in the food. I prefer mine in a glass.
If you are using a wine (an option in the tips of the recipe card), I suggest a non-sweet, dry white, or red wine. A few suggestions: Sauv Blanc, Semillon, Pinot Grigio, Chardonnay, Merlot or Pinot Noir.
French Onion Soup is from France in the 18th century; this traditional French soup can be used as an appetizer or a main course. Part of the reason for the initial popularity was that onions were cheap and readily available.
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Crock Pot French Onion Soup
- 1 ½ pounds onions - about 3 medium size onions
- 1 teaspoon coarse salt
- 2 tablespoons butter
- ½ teaspoon pepper
- 1 ½ teaspoon Worcestershire sauce
- ½ teaspoon thyme
- 4 cups beef broth
- ½ cup Wine - optional
Finishing then serving
- Crusty bread
- Cheese of choice for topping
- Chop 1 ½ pounds of onions, about 3 medium size onions. Some people will want rings or petals—add to a 2 ½ quart or larger crock pot. 4 quarts or a larger crock pot are needed if doubling the recipe. Triple needs larger than 6 quarts.
- Add 1 teaspoon of coarse salt, 2 tablespoons of butter, ½ teaspoon of black pepper, 1 ½ teaspoon Worcestershire sauce, and ½ teaspoon of thyme. Then stir them together. The butter can go in unmelted, but you must stir in 1 hour or melt it in the microwave.
- Cook on high with lid on for 9-10 hours until nicely darker brown. Be warned that some crock pots may run hot, and please watch for the endpoint of "softened and deep golden brown" for the onions being done, and don't go by time alone. Then add 4 cups of beef broth and cook on high for at least one hour. Toast slices of crusty bread·butter, and bake.
- Preheat the broiler to high. Arrange ramekin or oven-safe bowls on a cookie sheet. Ladle hot soup into the bowls, and float toasted crusty bread on the soup.
- Cover each bowl with cheese of your choice.
- Broil until cheese is bubbly and golden, 2-4 minutes.
Your Own Private Notes
- Be advised that some crock pots may run hotter so watch for softened and deep golden brown as the endpoint for the onions being done. I would say if your crock pot ever boils on low, it may be in the "runs hot" category, then use low for this recipe. More discussion in the post.
- Also, using a much larger crock pot for this small recipe may cook a bit faster.
- Please check the onions halfway through due to the above.
- This recipe can be easily doubled but could also be cut in half.
- This makes about 6 cups of soup. I call that 4 servings of 1 ½ cups each.
- As written, use a 2 ½ to 4-quart crock pot. For a double recipe, you will need 4-quart or more. A triple recipe fits in a 6 quart or larger.
- Some type of crusty bread is used to float cheese on top. You can use what you want, but a nice crusty French baguette is my choice. For the cheese we like provolone, but some prefer Gruyere or Swiss.
- Quality matters here in the choice of broth. Do not cheap out on generic.
- Wine can be added to the soup with the broth. A half cup would be about the right amount. Suggestions discussed in the post.
- Good refrigerated for 3-4 days and 3-4 months frozen.
To adjust the recipe size:
You may adjust the number of servings in this recipe card under servings. This does the math for the ingredients for you. BUT it does NOT adjust the text of the instructions. So you need to do that yourself.
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Editors Note: Originally published July 12, 2015. Updated with expanded options, refreshed photos, and a table of contents to help navigation.
This recipe is part of Our Best Soups.