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Slow cooker caramelized onions are irresistibly good with a splash of balsamic vinegar and are easy to make in a crock-pot. Effortlessly elevate your next dish.
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I'm tearing up. But my eyes aren't watering from all the onions I just sliced! I have tears of happiness because I have lots and lots and lots of caramelized onions stashed away in the freezer.
And, I love caramelized onions. Using them in a dish is such an easy, healthy, and low-carb way to add richness and flavor. I use them in everything from Greek yogurt caramelized onion dip to vegetable dishes.
I recently posted a recipe for pumpkin flatbread pizza and made caramelized onions the traditional way. I don't often have time to stand over the stove top and keep vigil over the onions, though. The entire time, I wistfully glanced over at my freezer and wished some caramelized onions were stowed away.
It was time to pull out the crock-pot and restock.
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Ingredient Notes
You'll need the following ingredients to make caramelized onions in a crock-pot.
- Onions - I used yellow onions for a classic sweet result. White onions are less sweet but will work. Sweet onions, such as Vidalia onions, have more sugar and are also a great option. Or use a combination of different types of onions!
- Olive oil - Add oil to coat the onions so they don't stick to the crock and have a silky smooth texture.
- Balsamic vinegar - For the most part, I make caramelized onions in the crock-pot like everyone else does. The one thing I do just a bit differently than most...I stir in a splash of balsamic vinegar towards the end of the cooking time. It enhances the color and taste. But it doesn't overwhelm the onions at all.
The recipe card below includes ingredient amounts, step-by-step instructions, and nutritional information.
Yield
Three pounds of yellow onions yield two to two and a half cups of caramelized onions!
How to make slow cooker caramelized onions
The pictures below will help guide you in making this recipe:
Step 1
Peel and cut onions in half. Then, slice the onions uniformly with a mandolin or knife and place them in a slow cooker. I used setting three on a mandolin.
Step 2
Drizzle the onions with olive oil and toss to coat. Cover and cook on low for 10 hours. Stir occasionally, if desired, to prevent sticking.
Step 3
Remove lid and stir in balsamic vinegar. Return the lid and leave it ajar to allow the liquid to begin evaporating.
Step 4
Remove the onions from the slow cooker and place them in a colander to drain off the liquid. Retain the onion juice for another use.
Tips for Success
- Ideally, use a 5- to 6-cup slow cooker. The onions will completely fill a 4-quart slow cooker. If the crock-pot is any larger, they will cook too quickly.
- Slice the onions evenly so they caramelize at the same rate.
How to Freeze Caramelized Onions
Let caramelized onions cool, then spoon them (with their juices) into an ice cube tray or small freezer bag. Freeze until solid, then pop out the cubes or flatten the bag for easy storage. They’ll keep for up to 3 months and can be added straight to soups, pizzas, or veggies.
FAQ
We recommend cooking them on the low setting, which allows their natural sugars to release slowly, resulting in deep, sweet caramelization. You can use the high setting for 4–6 hours if you’re short on time, but the onions may brown unevenly and won’t be quite as rich. For the best of both worlds, start on high for the first hour, then switch to low for the remainder of the cooking time.
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📋 Recipe
Slow Cooker Caramelized Onions
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Equipment
Ingredients
- 3 pounds yellow onions
- 2-3 Tablespoons olive oil
- 1 Tablespoon balsamic vinegar
Instructions
- Uniformly slice onions with a mandolin or knife. I used setting 3 on a mandolin.
- Place onions in slow cooker and drizzle with olive oil. Toss to coat all the onion slices.
- Cover and cook on low for 10 hours.
- Remove lid and stir in balsamic vinegar.
- Return lid and leave ajar to allow liquid to begin evaporating.
- Cook for 1 hour more on low.
- Remove onions from slow cooker.
- Place onions in a colander to drain off liquid. Liquid can be retained for another use.
- Portion and freeze onions in a freezable containers or plastic bags according to needs. ¼ cup portion sizes work well.
Notes
Nutrition
This recipe was originally posted on October 9, 2019, and has been updated to improve the user experience.
Nutmeg Nanny says
I love making caramelized onions but they get even better when made in the slow cooker. So easy!
Martha @ A Family Feast says
I'd like to eat some of those onions - just with a spoon! Those look seriously yummy! And never thought to make them in a slow cooker either - great idea!
Jordan @ Smile Sandwich says
I've always wanted to try caramelizing onions my slow cooker! Adding balsamic is such a good idea and so easy.
Rebecca @ Strength and Sunshine says
Great! So easy and so many possibilities!
Heather // girlichef says
I love the slow cooker caramelization method, I use it for garlic sometimes, too! It's so nice just to be able to let it happen all by itself and have a big batch ready to enjoy later. They look great, Marjory!
Beth @ The First Year says
It's so nice to be able to get them all cooked at once, less tears in the end!
Marion@Life Tastes Good says
I am learning so many wonderful slow cooker tips today! I LOVE caramelized onions! They make most everything better, but I never knew you could make them in the slow cooker! I don't use my slow cooker a whole lot, but you can be sure I will be making some caramelized onions in it, and I love your tip on adding the balsamic - yummm. Thanks, Marjory!
Betsy @ Desserts Required says
You are BRILLIANT! I never would have thought to caramelize onions in a crockpot. Not only is this a breeze to do but the ease of freezing the onions and then simply pulling them out when needed is fantastic!
MealDiva says
Yum! Those are some great looking onions!
The Ninja Baker says
Grrrreat idea to make a whole bunch of caramelized onions, freeze them and have them ready to go!
susan // the wimpy vegetarian says
I make caramelized onions all the time and can attest that adding balsamic vinegar is the way to go. It's amazing how their flavor transforms with it. But I've never made them in my slow cooker. FABULOUS idea.
Tara says
This is brilliant!! What a great idea to have these at the ready in your freezer, I love caramelized onions. I have to do this for sure!! Love the added balsamic at the end!!
Lea Ann (Cooking On The Ranch) says
Well, this just made caramelized onions a more frequent visitor to my meals. I love them and so many times don't have the 45 minutes it takes to fuss over them stovetop. Thanks so much for this recipe and love that splash of balsamic. Nice cooking with you for #SS
Renee says
I'd have tears of joy too with knowing those yummy caramelized onions are in the freezer waiting to be used on so many things.
Hezzi-D says
Love that you can caramelize onions in the slow cooker! This would be perfect when making French Onion soup because the onions would be ready when I get home from work!