Slow Cooker Caramelized Onions

You’ll never believe how easy it is to make perfect caramelized onions in a slow cooker. They’re sweet, savory, and oh so delicious!

You can make these onions ahead of time and store them in the fridge, or freeze them for later use. That way you’ll always have caramelized onions on hand!

A small blue bowl filled with slow cooker caramelized onions on a white marble background.

Slow Cooker Caramelized Onions take the traditional method of caramelization to a whole new level!

Caramelizing your onions in the slow cooker takes much longer than on the stovetop but it’s totally worth it for the intensified aromatic flavor and depth of golden brown color you get from slow cooking them.

Plus, it’s completely hands-off. You can literally prep your onions, set your slow cooker and get on with the rest of your day without having to babysit any of the cooking! Properly caramelizing onions on the stovetop takes forever so I love this set-it-and-forget-it option.

An overhead view of the ingredients needed to make caramelized onions in a slow cooker: just thinly sliced onions and a pat of butter.


To make caramelized onions in your slow cooker, you only need 2 ingredients:

  • Yellow Onions. You’ll want to stick with using yellow onions for this recipe since they are the best for caramelizing and have a nice sweetness that other types of onions don’t. If you like sweeter onions, you can throw a Vidalia or two into the mix, but using all sweet onions can be pretty overpowering.
  • Butter. A pat of butter gives these onions their delicious flavor. You can use either salted or unsalted butter for this recipe, so go ahead and grab whatever you have in the fridge!

Slow Cooker Caramelized Onions Tips and Variations

  • Easily double this recipe if you require additional caramelized onions for recipes and meals. 
  • You can use olive oil instead of butter when making your caramelized onions. While there’s no exact ratio for replacing butter, a good rule of thumb is to use ¾ the amount of butter called for in the recipe. Since my recipe calls for 1 Tablespoon of butter, if you opt for olive oil then use around ¾ Tablespoon of oil.
  • While it’s not necessary, you are welcome to add some salt (about ½ teaspoon) to your onions before cooking. 
  • Don’t add any additional liquid! It might seem unusual nto to add any liquid to your crock pot before turning it on, but the onions will release plenty on their own once they start to heat up.

After 10 hours of slow cooking, your onions should reach that beautiful golden brown color and have lost most of their liquid. If you love jammier caramelized onions with a deeper color, then continue cooking on LOW for another 3-5 hours, keeping the lid of your slow cooker slightly ajar for the liquids to evaporate.

Pro Tip: Make sure to check on your onions every hour if you’ve opted for a longer cooking time and stop cooking as soon as you’re happy with the consistency and color of your onions. 

Hot to store slow cooker caramelized onions

Whether you have leftover caramelized onions or you plan on making your onions ahead of busy times, you’ll be happy to know that they can easily be stored in the refrigerator or the freezer.

In the refrigerator:

Store your caramelized onions in the refrigerator for up to 1 week. To reheat, simply add them to a microwave-safe bowl and reheat for 20-30 seconds or add your onions to a skillet over medium-low heat for just a few minutes, paying careful attention that they don’t burn. 

In the Freezer:

Your Slow Cooker Caramelized Onions will freeze well for up to 3 months when stored in an airtight container. When ready to use, thaw overnight in the refrigerator and then reheat as you would have if they were refrigerated.

Whether you opt to store your caramelized onions in the fridge or freezer, make sure they have completely cooled first before transferring them to an airtight container for storage. You’ll also want to keep the remaining liquid from the slow cooker separate from your stored onions – it’s super delicious to use in other recipes as a broth and can also be refrigerated or frozen for later use!

Can I leave my onions unattended?

Absolutely! While your onions are cooking in the slow cooker on the LOW setting for 8-10 hours, you don’t need to supervise the cooking at all.

With that said, if you are around your kitchen you can definitely check on your onions and give them a stir which will help to cook them more evenly but this is totally up to you!

You might not be able to stop peeking since they’ll fill your house with a completely irresistible aroma, but try not to open the lid too many times since it can affect the cooking process.

Recipes To Use These Caramelized Onions:

Use these sweet and jammy caramelized onions as a topping for homemade pizza, tarts, or over various meats. Try stirring them into your favorite macaroni and cheese — it’s out of this world.

Here are a few more options:

You can also add beef broth to transform them into a fantastic onion soup like I did in my Slow Cooker Meal Prep Cookbook! Or add a tablespoon or two of balsamic vinegar as they cook for an easy twist on my onion jam recipe.

Overhead view of a blue bowl filled with slow cooker caramelized onions on a white background.You’ll never believe how easy it is to make perfect caramelized onions in a slow cooker. They're sweet, savory, and oh so delicious! You can make these onions ahead of time and store them in the fridge, or freeze them for later use. That way you'll always have caramelized onions on hand!
Slow Cooker Caramelized Onions

Slow Cooker Caramelized Onions

Yield: 1 1/2 cups
Prep Time: 5 minutes
Cook Time: 10 hours
Total Time: 10 hours 5 minutes


  • 5 yellow onions, thinly sliced
  • 1 tablespoon butter


    1. Add the onions and butter to your slow cooker
    2. Cover the slow cooker and cook on low heat for 8-10 hours, until the onions are deeply caramelized and fragrant. To help prevent burning, give them an optional stir after about 6 hours.

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Nutrition Information
Yield 6 Serving Size 1/4 cup
Amount Per Serving Calories 51Total Fat 2gSaturated Fat 1gTrans Fat 0gUnsaturated Fat 1gCholesterol 5mgSodium 18mgCarbohydrates 8gFiber 1gSugar 4gProtein 1g

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By on August 24th, 2021

About Lauren

Hi, I'm Lauren! I'm a certified plant-based cook and enthusiastic omnivore who loves looking for creative ways to make weeknight meals more nutritious. I'm the author of Heathy Eating One Pot Cookbook and Healthy Meal Prep Slow Cooker Cookbook.

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