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.
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
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Nutrition
This recipe was originally posted on October 9, 2019, and has been updated to improve the user experience.
Sarah says
We made this and used it all up on pizza so I'm off to make my next batch! Thanks for recipe.
Angela {Mind Over Batter} says
I will be crying tears of joy once I slow cook my onions to caramelized perfection! I never even considered doing this in my slow cooker! THANK YOU, THANK YOU, THANK YOU!!!
Kim Beaulieu says
This is one of my favourite things to make in my slow cooker. It's so good to put on top of sandwiches and whatnot. This makes me want to whip up a batch immediately.
Amanda @The Kitcheneer says
Great idea! I love that it's a slow cooker recipe and a freezer recipe all in one! Totally digging adding some onions on my pizza!
Karissa | Sweet as a Cookie says
I'd be tearing up from cutting the onions and the happiness of caramelized onions in my freezer 🙂
Kirsten/ComfortablyDomestic says
Why have I never made caramelized onions in the crock pot?! I'm a fiend for caramelized onions...a FIEND! Having a stash in the freezer would be awesome.
Sarah Walker Caron (Sarah's Cucina Bella) says
I had no idea that you could caramelize onions in the slow cooker! OMG - WOW!