Classic French onion soup features beefy broth loaded with caramelized onions with crusty bread and melted cheese. Elegant comfort food made ridiculously easy with your slow cooker. Perfect for a small crock pot or double to make the family size.
Introduction
Better than restaurant quality, this crock pot French Onion Soup is perfect for everyday or special meals.
I love good French onion soup. I mean really love it. If it's on the menu, I usually make sure I have it.
Unfortunately, that means the good, the bad, and the ugly. I should put adequate on that list too. I can live with adequate, but most seem to be wanting and falling into the bad/ugly range.
My Rating
Very nice solid lower 5. You can make a little better French onion soup but with more work. This is much better than most restaurants. I have had only a few better.
❓What is French Onion Soup?
From the 18th century, this traditional French soup can be used as an appetizer. But I love a bigger bowl for the main course.
Good onion soup is more than a beef broth with some onions. You need to get the caramelization going well, or you have nothing. You need some long cooking to get there.
Caramelization is the browning of sugar through the oxidation of those sugars. When correctly done, it results in a deep nutty flavor and brown color. Just what we need for a great soup
While many techniques require multiple rounds of caramelization on the stovetop, 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 a long time, add the broth, and cook a little longer. Then serve your favorite way. Yum.
🧅Ingredients for French Onion Soup
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 best. I consider white and red onions equivalent to my usual yellow onions, and some people like a mix.
Sweet onions like Vidalias, Mauis, and Walla Wallas are probably not a good idea here. I don't like much sweetness here, and that may spoil the broth. But some people prefer the sweetness of these onions and may even add sugar, so your choice.
Seasoning and Worcestershire sauce
The seasoning is limited to some thyme with salt and pepper.
Worcestershire sauce will make the "beef" flavor pop. It can be used in many cooking applications to boost that beef test, especially when using beef broth.
I'm using Lee and Perrins Worcestershire Sauce, which I trust, but I suspect there are other good choices.
Beef Broth
Very few commercial beef broths or stocks are above adequate, and many are just bad.
I like Swanson broth. It has improved in quality over the years and is quite good now. The Swanson stock is also good, but I detect no difference in use, so I don't spend the extra money.
You can do home stock or broth. It is easy to make and store but is not this recipe. It seems a little the top for a crock pot soup.
Wine is not required for onion soup.
Wine has traditionally been used to de-glaze the pan after caramelizing the onions—not really needed with a crock pot. But the wine also added flavor to the soup.
Never cook with a 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.
👨🍳How to Make Onion Soup in a Crock Pot
- Trim 1 ½ pounds of onions (about 3 medium onions) into rings or petals.
- Add the onion to a 2 ½ quart or larger crock pot with butter and seasonings.
- Cook on high for 9 to 10 hours to carmalize. This is variable depending on you crock pot. Check early several times.
- Add beef broth and cook one more hour on high.
- Serve usually with crusty bread and topped with cheese browned under a broiler.
♨️What Crock Pot to Use for Onion Soup
This recipe can be easily doubled but could also be cut in half. 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 fine but may cook a bit faster.
So this fits well in a small crock pot of 2 quarts minimum. Double recipes (what I suggest making) need 4 quarts or bigger.
Trouble shooting 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 crock pots and their temperatures a bit.
On a crock pot, both low and high should be 212° range and take a different time to get there. That is all controlled by a thermostat that has improved over the years.
Some crock pots (especially older ones) can run over 300°, 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 your crock pot boils on low, it may be in the "runs hot" category, then use low for this recipe.
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. So right size crock pot is important, or watch the endpoint carefully.
My 9-10 hours on high stands and is consistent with other similar recipes and less than Cooks Illustrated, which is 10-12 hours on high.
❓FAQs
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.
You can use what you want, but a nice crusty French baguette is my choice.
Some crusty bread is used to float cheese on top. You can skip it, but it is traditional and helps keep the cheese on top.
The bread must be toasted to prevent a sloppy mess. I use thinner slices, but many like cubes of bread, more like large croutons.
❄️Storage of French Onion Soup
Store in an airtight container. Good refrigerated for 3-4 days and 3-4 months frozen.
📖Crock Pot Soups
Crock Pot Ham Bone and Bean Soup
Crock Pot Broccoli Cheese Soup
Thick Crock Pot Cheeseburger Soup
This recipe is part of Our Best Soups.
This recipe is listed in these categories. See them for more similar recipes.
🖼️Step-by-Step Photo Instructions
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 some petals—add to a 2 ½ quart or larger crock pot. If doubling the recipe, a 4 quarts or larger crock pot is needed. Triple needs larger than 6-quarts.
Add one teaspoon coarse salt, two tablespoons of butter, ½ teaspoon pepper, 1 ½ teaspoon Worcestershire sauce, and ½ teaspoon thyme. Then stir together. The butter can go in unmelted, but you will need to stir in 1 hour or melt it first in the microwave.
Cook on high for 9-10 hours until nicely darker brown. Be warned that some crock pots may run hot, and please watch for the endpoint and don't go by time alone. Using a larger crock pot may also lead to cooking too rapidly. Then add 4 cups of beef broth and cook on high for at least one hour more.
Preheat 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.
📖Recipe
Crock Pot French Onion Soup
Ingredients
- 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
- Crusty bread
- Cheese of choice for topping
- ½ cup Wine - optional
Instructions
- Chop 1 ½ pounds of onions about 3 medium size onions. Some people will want rings or some petals—add to a 2 ½ quart or larger crock pot. If doubling the recipe, a 4 quarts or larger crock pot is needed. Triple needs larger than 6-quarts.
- Add one teaspoon coarse salt, two tablespoons of butter, ½ teaspoon pepper, 1 ½ teaspoon Worcestershire sauce, and ½ teaspoon thyme. Then stir together. The butter can go in unmelted, but you will need to stir in 1 hour or melt it first in the microwave.
- Cook on high for 9-10 hours until nicely darker brown. Be warned that some crock pots may run hot and please watch for the endpoint and don't go by time alone. Then add 4 cups of beef broth and cook on high for at least one hour more.
- Preheat broiler to high. Arrange ramekin or oven-safe bowls on a cookie sheet. Ladle hot soup into the bowls, float toasted crusty bread on sou
- Cover each bowl with cheese of your choice.
- Broil until cheese is bubbly and golden, 2-4 minutes.
My Private Notes
Recipe Notes
Pro Tips
- 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 double 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.
Nutrition Estimate
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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.
joan
Recently made this. Turned out great. So much easier than slowly cooking onions on the stove. 9 hours on high was good. Will be making onion soup a lot more now.
DrDan
Hi Joan and Happy Holidays
This does turn out a great soup. Once you know your crock pot, this is a put it on in the morning and have a great dinner type recipe.
Thanks for the note.
Dan
Melanye
Does the cook time change if using a larger crock pot?
DrDan
General rules are that too small may prolong cooking time if more than 75% full. Too big is usually considered fine. BUT here we are prolonged cooking on high. I would expect it to cook faster. And if you have one of those pots that boils on low (IE a hot pot) we could be burning the onions. If in doubt, cook on low and look for the end point of soft and deep golden brown.
Dan
Lisa Huff
Oh wow, this looks so good!
Mary
I've had mine cooking for 2 hrs so far and my house smells Ah-MAZING! Can't wait for dinner tonight.
Mary
It didn’t disappoint! No burnt onions even cooking on high for 9 hrs. Perfectly carmalized and a fantastic soup!
Emily
I made this recently and it was SO easy and delish! I ended up buying jarelsburg cheese. I will make this again for sure!
DrDan
Thanks for the note. It is one of my favorite soups.
Dan
Chris
At what point to you add the ingredients from 2nd crock pot? 😊
DrDan
No second crock pot. Carmalize onions then add broth and cook some more. Then is ready to put into bowls with bread and cheese.
Dan
Colette Watts
Before I make this can you freeze the soup.
Tks
DrDan
Yep
Cera
Cut a huge portion of time off by quickly caramelizing your onions in butter prior to adding to the crock pot. Adds a ton more flavor and onions are not mush.
Paige
What kind of cheese and bread do you prefer to use? And how much of each?
DrDan
I like a crusty French or Italian bread with Provolone cheese. About 1/2 to 3/4 inch thick slice of the bread to cover the dish and just enough cheese to cover also.
Jennifer
Should I use yellow onions??
DrDan
Yellow or white.
Nicole
So I'm like Dan, mine burned a lil. I started it at 730am, it is now 111pm can i add the broth and let it sit on low all day? The onions are pretty camerlized but my husband and son don't get home till about 5pm
DrDan
I think some crock pots run too hot for this recipe on high. With your pot, do low next time. Remove from heat now since they are caramelized and refrigerate. Then about an hour and a half before you need it, add the broth and cook on low. It does need to simmer some with the broth and not just reheat.
Willie Mitchell
Sound delious.. Only thing I dislike onions ?
Dr. Horshenschwartz (from the clinic)
Excellent. Made it a couple months ago, making it again today with 6 pounds of onions. Smells amazing!
Dan
You must have a typo. When you cook onions on high for 9 hours you get burnt onions. I know because I did it. I'm mad that I didn't use my own common sense. You should change that to say LOW for 9 hours. Please fix this so others like me dont have their whole house smelling of burnt onions.
DrDan
Hi Dan...
Sorry it didn't work well for you but high is correct. I did it twice and 9 hours on high worked great in two different pot I have. I check some references before I replied and they are all over the place. 8 hours on low to 14 hours on high. Cooks Country does high for 10-12 hours...
So what went wrong. 1) your crock pot runs hot and/or 2) some variation in the onions.
I'm putting an advisory on the recipe stating to cook to "softened and deep golden brown". You want the caramelization.
Thanks for the note
DrDan
Paula Mencucci
I had the same problem. Burnt onions....I'm sad because I use the crockpot when I"m not home to cook and when I come home after a long day to ruined dinner, I'm extremely disappointed :( Apparently my crockpot runs hot, but only on one side...
DrDan
Hi Paula,
I changed some wording about hot pots. I believe it was Crock Pot brand that had the heating element located in one location near the front if I remember right and not around the pot. They had a lot of localized burning from what I understood.
The warning I added about hot pots was if you see boiling when cooking on low, then you should assume a hot pot. On low a crock pot should be 207 or less. Most run right at 200. It is harder to measure the temperature on high since it should be about 250 but some pots run 300. Since both are above the boiling point you can't get an accurate measurement without special equipment. That, of course, does not address hot localized spots.
Again, sorry you had an issue.
Dan
Kathy Heiber
This is delicious....I have always loved French Onion Soup and now I can have it whenever I want....YAY!!!
rating...+10
Peg
Do you leave it covered or open?
DrDan
Covered.
Steven House
I LOVE french onion soup, but rarely make it since caramelizing the onions is almost a day long affair. For some reason I never considered using my crock pot. I can't wait to try this. Many thanks!
Cheryl S.
LOVE the onion soup. Even my very picky 10 year old gave it a definite thumbs up! Who knew it could be so easy?!?
DrDan
Thanks for the note and rating. I have repeated this several times.