How to Make Caramelized Onions in Your Slow Cooker

I am falling more and more in love with my slow cooker. It’s amazing what complex things you can do with one simple kitchen tool! First it was homemade yogurt and now it’s caramelized onions. Yes, you’ve read that right. I have now discovered how to caramelize onions in my slow cooker. Like the yogurt, it takes time but so little effort. You’ll be amazed at how simple it – and how tantalizing your house smells as the onions cook.

Have you used caramelized onions before? I’ve started using them in the past year because a little bit adds a big flavor to my dishes. I started making them for patty melts but now stir them into countless things. I like to toss them in with some sauted peppers, beans and corn for a tasty veggie burrito. I also put caramelized onions on my grilled cheese sandwiches, any type of panini, and even with my homemade macaroni and cheese. It’s a classy way to dress up simple meals. And of course, you need caramelized onions to make french onion soup!

Onions are cheap so there is little expense for big flavor. It’s a great frugal cooking trick. I recently picked up 3 pounds of yellow onions for $1 and gave this a try. It worked perfectly the first time and I’ve made several more batches since then. Normally, you have to stand watch by your stove for a good 45 minutes to get truly caramelized onions. With your slow cooker, you can toss the onions in and leave them all day to caramelize to perfection.

The other wonderful thing about this method that you can make a large batch of caramelized onions in your slow cooker and then freeze them for future meals. I freeze them in 1/2 cup serving sizes. I scoop the onions into a square of foil, roll them up and freeze them until I need them. They taste just as good when they are thawed!

It takes 3 simple steps to make caramelized onions in your slow cooker. Here’s what to do.

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Caramelized Onions in Your Slow Cooker. First, Peel your onions.

First, peel your onions and slice the ends off. This is the most time consuming part and yes, tearful part. Just remind yourself that by doing a large batch at once, you’re saving yourself tears later! You can do as many onions as fit in your slow cooker. I have found that a 3 pound bag is the perfect size for my regular slow cooker.

Caramelized Onions in the Slow Cooker. Put onions in the slow cooker all day.

Next, slice your onions. If you have a (food) mandolin, you can make quick work of this task. I just got one this Fall and am loving it! Otherwise, use a sharp knife and slice your onions in 1/4 inch rounds. Don’t worry about separating the rings of onions. They will fall apart as you toss them in the slow cooker.

Put a stick of butter in the bottom of your slow cooker. (It works with a half stick too, but I think the onions caramelized a bit nicer with a full stick.) Toss all the onions on top. Put the lid on. Turn your slow cooker on low and leave it to cook for 8 to 12 hours. 8 hours is the minimum but the longer they sit, the more they will caramelize. You can stir them once or twice if you would like to prevent any sticking but it is not necessary.

Caramelized Onions in the Slow Cooker. After all day cooking, you'll have no fuss, beautiful, caramelized onions!

Now you’re done! Wasn’t that simple? The hardest part is waiting as you smell the onions cook all day. You can use them right away or freeze them for future use. I recommend freezing the onions in small portions so you can easily get out what you need.

What do you think? Will you give this a try? For what do you use caramelized onions?

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  1. I just made these onions this past weekend. I used Sweet Vidalia onions…put them on while we were gone for the day…oh my how good the house smelled when we returned! I could have eaten the whole batch right out of the crockpot! Or added some beef broth and had a tasty onion soup. Soooo good. Thanks for sharing!

    1. Oh, Addy, I’m so glad you liked them! My husband said the same thing the first time he walked in the door and smelled the onions cooking. I’ve turned the pot into onion soup, too, and it is such an easy way to do it. You’ve reminded me that I need to make another batch soon because I only have a little bit left in the freezer.

  2. Love this! I am going to try making this sometime this week. I had a bunch of onions go bad on me recently, would have been nice to do this!

    1. Ugh. I hate it when food goes bad. I’m trying to be better at using it up before it does – or utilizing my freezer more. The nice thing about this is that I can caramelize the onions to use them and still freeze them if I need. I hope you like them as much as I do, Vera!

  3. I am trying your lunch idea! The red onions where awesome in the crock! To think how much time I spent doing it on the stove!?!

    I do have a really sensitive nose and it’s not uncommon for me to move my crocks outside if something it too strong for me. I did end up moving them outside, but it was so worth it! So simple!

    Thanks for a HUGE time saver for some onion lovers!

    1. The onions do smell up a house as they caramelize all day. My husband gets hungry for patty melts with onions when he smells them cooking! 🙂 I’m so glad it worked and saved you so much time. Enjoy your delicious onions!

  4. I am trying this now! With red onions. 🙂

    You seem to like sweet potatoes and one of my favorite ways to eat them is baked, cut in to chunks sprinkled with a tbsp of EVOO, and some ancho or cayenne pepper or both… It’s delicious! It started as a sweet potato black bean chili I make, but we ate so many before I ever got to make the chili, so now I just make them as a side. Any favorite spice would be good, but the sweet and spicy is amazing!

    1. Ohh! Let me know how it turns out with red onions, Christina! I had some of my caramelized onions from the freezer for lunch, sauteed with some peppers, corn and beans, in a tortilla. Love the idea for sweet potatoes! Nathan really likes them too. We’ll have to give that a try.

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