Easy Crock Pot French Onion Soup—Long and Slow

Dec 12, 2022 · Modified: Jun 1, 2023 by Dan Mikesell AKA DrDan · 71 Comments

4.31 from 250 votes

Classic French Onion Soup features beefy broth loaded with caramelized onions. Cooked all day in your crock pot, then topped with crusty bread and melted cheese.

bowl of onion soup covered with browned cheese.

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👨‍🍳How to Make French Onion Soup in a Crock Pot
🧅Ingredients
Caramelizing onions in a crock pot
♨️About the crock pot
❓FAQs
🖼️Step-by-Step Photo Instructions
Recipe

This elegant comfort food is as better as most restaurants, and you made it for pennies at home. Perfect for a small crock pot or double to make the family size.

Excellent onion soup is more than a beef broth with some onions. You need to get the caramelization going well, and that takes time. Let it cook all day to fully caramelize your onions for this soup's full depth of flavor.

French Onion Soup is from the 18th century; this traditional French soup can be used as an appetizer or a main course.

This recipe is part of Our Best Soups. Let's keep that crock pot out and try some 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.

👨‍🍳How to Make French 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 caramelize. This is variable, depending on your crock pot. Check early several times. Please see the section on crock pots below.
Add beef broth and cook one more hour on high.
Serve usually with toasted crusty bread and topped with cheese browned under a broiler.

🧅Ingredients

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.

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.

Caramelizing 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

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 9-10 hours, but this may be a few hours less or more depending on your crock pot.

♨️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 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.

A few readers have had burnt onions, but 9-10 hours on high consistent with other similar recipes and less than American Test Kitchen (subscription required), which is 10-12 hours on high.

❓FAQs

What cheese to use to finish?

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.

What bread to use?

You can use what you want, but I choose a nice crusty French baguette.
Some crusty bread or large croutons are used to float cheese on top. You can skip it, but it is traditional and helps keep the cheese on top.

How to store French onion soup.

Store in an airtight container. Good refrigerated for 3-4 days and 3-4 months frozen.

Is wine needed?

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.

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 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.