Foolproof Caramelized Onions in the Crockpot

Onions rock my world. They are inexpensive, delicious, make other foods delicious, and are good for you. They are chock full of allicin, which may help lower cholesterol and blood pressure (high blood pressure can be dangerous to both moms and fetuses); they are also a great source of vitamin C, fiber and folate. But, most of all, onions just taste amazing, raw or cooked, sliced or chopped. I put them in everything. And you should, too.
I channeled the Dutch masters for this photo, right?
Even if you're not President of the Onion Admiration Society, you will like caramelized onions. They somehow make every dish both earthy and gourmet. They are sweet and rich and you can put them in (or on) practically everything: steaks and burgers, soups, casseroles, sandwiches, salads, mujadarrah. Kids who are picky about raw onions will surely chow on sweet caramelized onions when they're in a meatloaf or scrambled eggs or on pizza.

The only problem with caramelized onions is that they can be a bit of a pain to make. They're not difficult, exactly. You basically fry them low and slow, with a lot of tending. But if you cook them a bit too long or don't tend them quite enough, they can easily burn. 

But if you cook them in a slow cooker? No burning. Just loads and loads (more than you could make in a standard frying pan) of gorgeous caramelized onions. Most recipes call for a stick of butter. I found that a bit of extra virgin olive oil worked wonderfully.

First I greased my crockpot with a bit of EVOO. I then quartered and sliced four pounds of onions (that's the amount of slices that fit in my crockpot):
Then I drizzled 1/4c of EVOO on top and tossed around to coat a bit.
Set on low and cook for 12-14 hours (or until they are at the level of caramelization you prefer), stirring every couple of hours or so.
About seven hours in...
About 10 hours...
I like my onions very caramelized, so I cooked mine for 14 hours. They were dark and rich, with a gorgeous onion syrup. I turned off the slow cooker and, while the onions were still hot, drizzled some balsamic vinegar on top, which was drunk immediately by the onions. (The balsamic is totally optional, by the way.) I also added some sea salt, to taste.
Balsamic caramelized onions
My four pounds of raw onions yielded about four cups of caramelized onions. I put two cups in a container in the freezer (to be used in soup soon) and two cups in a glass jar in the fridge to be used as a condiment on, well, everything I can think of. First thing I thought of: peasant bread + fresh mozzarella + caramelized onions = divine grilled cheese sandwich!

Looking for more ways to use your slow cooker? Try our Crockpot Applesauce!

UPDATE: Lisa's Dinnertime Dish featuring our slow cooker caramelized onions in her recipe for French Onion Soup. Thank you, Lisa!

This post contains affiliate links, so I make a small commission if you purchase through my links—which helps to keep this blog running.  



Comments

  1. oh, yum! another good use for my crockpot. one time, i let my onions go too far and that's how i discovered how to make my own French's Fried Onion (the best part of Thanksgiving, as far as I'm concerned!). i didn't have enough moz to make this sandwich today, so instead i made a mushroom and caramelized onion quesadilla. nom!

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  2. Was your quesadilla as yummy as it sounds? I love mushrooms, too...

    I have never actually had French's Fried Onions! Are those the things that one puts on green bean casserole (which i have also never had)?

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  3. omg, you've never had green bean casserole? i mean, the kind i grew up with is your classic supermarket nightmare-- can of campbells condensed mushroom soup, bag of frenched green beans, french's fried onions but mmh, good! awhile back, cooks illustrated had a recipe for a from-scratch version of it. anyway, the fried onions are so good. so bad but so good.

    (quesadilla was yummy but quick... need to experiment with different cheese and aromatics.)

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  4. Nope, never. My mom was very food co-op, everything from scratch, etc. Did you ever try the from-scratch version of the casserole? Did it stand up to the yummy-but-bad semi-homemade version?

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  5. Great idea Justine we have a post planned on secret flavoring ingredients, will link to this. Genius with the slow cooker.

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  6. Lauren - Thanks, that would be great!

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  7. i made the caramelized onion and moz sandwich for henry and i, for dinner tonight. yum! i forgot to add the balsamic, though... the onions definitely needed an acid. oops!

    and to answer your question, no, i never made it. as is usually the case with cooks' illustrated, it involved many more steps than i have time, patience or energy.

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  8. I probably use them within a week, but i'm guessing maybe 2 weeks (especially if you add vinegar). Not tested, but an educated guess :-)

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  9. I'm about to make caramelized onions but I wanted to ask...how long do they keep in the fridge?

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  10. Thanks! And, yeah, i didn't realize how many adults/friends of mine don't like onions (even cooked!) Don't know what i'd do without onions and garlic. Must be my Italian and Jewish heritage ;-)

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  11. Fabulous!  By the way, it's not only kids who don't like onions--I can't stomach even the least bit of any raw onion, but sautee them up a bit and I love them!  And by the way, yes--your picture does really look like a Dutch painting.

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  12. Wow, cooking for 40 people!! Good for you, Cyndi, and thanks for trying this! 

    Yeah, i do sometimes finish the onions in different ways, depending on how i'm using them - whether i just drain them (as i did for the grilled cheese in the blog post), fry them a bit in some oil or butter to crisp them up, or include with the liquid (as i do for my caramelized onion soup, elsewhere on the blog). But having tons of them handy is more than half the battle! ;-)

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  13. Thanks for this.  I just made some to put into megadarra (lentils only).  It took 18 hours with my crockpot on low, but that was 7 lbs of onions.  Seemed about the right amount for the 5 lbs (minus 2 cups) of lentils too.  Making food for 40 people at a Memorial on Sunday.  Rice is a separate dish which is why I didn't add it.

    I would have needed to finish these up in a pan to get them drier or crispy, but that's okay because the bulk of the work was done.  I didn't mind them wet for this dish.

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  14. This is BRILLIANT!!! Totally doing this. My dad's wife HATES onions and I don't know how they eat anything in their house. I onionify (?) everything. Thanks for sharing this info!

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  15. Glad I found your cooking method here. I found your link on allrecipies.com . I was tired of making carmelized onion mush, these are perfect looking & better tasting than any other recipie I have tried, right now I'm trying frozen pearl onions to add to tomato soup. Thanks

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  16. Wonderful, so glad you like this recipe!

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  17. Yeah, i have no clue how people cook without onions (and garlic, for that matter)! I start everything with them and I'm not stingy with the amount, either ;-)

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  18. Also shared at Everyday Mom's Meals' linky: http://www.everydaymomsmeals.blogspot.com/2012/03/church-supper-29.html

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  19. What a great idea to save in the fridge or freezer for later use.  I will buy a bunch of onions this week and try this.
    Thanks so much for sharing your tip.  Peggy

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  20. Peggy, Thanks for posting! If you do try it, please come back and let us know how you like them :-)

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  21. Krista@Everyday Mom's MealsMarch 4, 2012 at 3:12 PM

    What a great idea! Never thought of doing them in the Crock- Pot! I love French Onion Soup and this would make that so much easier! Thanks for sharing at Church Supper. Have a blessed week & see you again next Sunday

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  22. Thanks for stopping by, Krista!

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  23. Cook's Illustrated says you shouldn't use sweet onions for French Onion Soup.  Since caramelizing them makes them sweeter anyway, I say why not?  From your photos it looks like you used yellow onions.  Any opinions?

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  24. I used Spanish/yellow onions. I never use the really sweet varieties, like Maui or Vidalia, in large part b/c i don't love them and so never have them in the house. My everyday onion of choice (for salads, etc) is a red onion; i have caramelized these and they're lovely but i think they have a lower water content, so I find that i need to add more oil and/or a bit of water if i'm doing them in the Crockpot. Hope this helps! Please let me know if you try them :-)

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  25. Could I leave the onions in the crockpot all day while I'm at work or do they really have to be stirred every 2thing hours?

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  26. Sweet onions are lower in all the good stuff that make onions taste like onions, that's what makes them sweeter than regular ones, so when they are caramelized the flavor isn't as rich, but rather insipid.

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  27. Hi! I wanted to let you know that I linked to your post. I just love this idea. Thanks for sharing it. http://lifecurrents.dw2.net/?p=7344 :)

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  28. Thanks so much, Debi! I'll head on over to check it out...

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  29. Also shared at Amee's Savory Dish's Fit & Fabulous linky party: http://www.ameessavorydish.com/2012/04/fit-and-fabulous-fridays-29.html

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  30. I would like to use these in a quiche this evening but do not have the time to cook them 12-14 hours.  Is there any reason I couldn't put my crock pot on high for a few hours to cook these?

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  31. fullbellysistersMay 8, 2012 at 4:48 PM

    Sorry, I'm not sure if i'm too late with the reply...but I can't say I've ever tried it. I think it might burn, but I don't know for sure. If you do try it, I would love to hear back on how it turned out!

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  32. Jane@whatare(we)having?September 9, 2012 at 9:23 AM

    I didn't know you could even use the slowcooker like that. I made my first batch & they are waiting patiently in the fridge for me to make a batch of your onion & mushroom soup. The smell wafting through the house while they were cooking was amazing! Thank you so much for bringing these into my life! x

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  33. Thanks so much, Jane! Hope you enjoy the soup, too!

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  34. I love the idea to make ahead and freeze. It could be a great timesaver for a weeknight dinner since I tend to start a lot of my meals with sauteed or carmelized onions. Any tips for how best to freeze (container etc.) and more importantly, how did you defrost them. Did you just put them frozen into a pan or did you let them defrost all day in the frig or what. I also fear these would end up like crock pot applesauce, great idea to freeze but soooo good never any leftover to actually make it into the freezer! Ha ha. Thanks!

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  35. I love the idea of making them in the crock pot! Thanks so much for sharing on my Crock Pot Thursday on Facebook!

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  36. I'd say 1-2 weeks in the fridge. I usually keep some in the fridge and then just freeze the rest in portioned containers.

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  37. I love caramelized onions (onion jam) I have a blog post dedicated to this! I never thought to make it in a crockpot! Great idea! I'm your newest follower! =D

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  38. Welcome and thank you, Lillian!

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  39. Would it be possible to substitute pearl onions for half (or more) of the onions? I had a salad with caramelized onion pearls once before, and it was absolutely delicious. :-D

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  40. I've never tried it, so Im not sure. But it sounds delicious! If you try it, will you let us know how it worked out?

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  41. When I made a batch, I used mostly larger onions broken down, but I also tossed in about 2 handfuls of pearl onions - they were delicious. If you're gonna do pearl onions, make sure you keep them closer to the bottom/sides of the pot so that they can be heated more thoroughly through and thus become more tender. I love this recipe for it's lack of butter and what-not. :D

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  42. Had to come back and say that I made these again in my slow cooker, and my house smelled so good when I woke up in the morning. I used them in a frittata with zucchini, and I also made a few more of those sandwiches! So good...

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  43. Thanks so much for reporting back :-)

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  44. Delicious!! super easy! I cooked mine for about 14 hours. Just as good as when I have done it on the stovetop and so much easier! The recipe also made so many more! Thank you!!

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  45. So glad to hear you liked them!

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