Caramelized Onions 1200

Caramelized Onions in a Slow Cooker

Why make caramelized onions in a slow cooker when it takes so long? Well, have you ever caramelized onions on the stovetop? First you melt butter in a big heavy pan, then you add a bunch of onions, and stand there, stirring and cooking, for an hour or more. Stand there. Stir. Monitor the heat. Check for any signs of burning. Stand there. Stir more.

Now how about this: put butter, onions, and herbs in your slow cooker. Cook for a couple of hours, stir once, then cook more, for hours and hours, blissfully unattended with no worries about burning. This is a better way!

Yes, it takes a long time. But it’s hands-off time; time you can spend doing something else.

Yes, it’s a big batch. So what? Caramelized onions freeze beautifully in 1 to 2 cup portions, meaning you’ll have them right when you need them, without all that stirring. You can use a cup of these onions, add some rich beef stock and some cheese toast, and end up with onion soup for one. I think that caramelized onions slow cooker style are a kitchen basic. They have a zillion uses from onion soup to caramelized onion pizza to perfect accompaniments to meatloaf sandwiches to … you get the idea.

A warning here: you’ll smell that enticing oniony mm, something’s cooking smell. If this bothers you (it really bothered the household cat) then you might set up your slow cooker on a porch or patio or even in the garage.

And a quick tip: Freeze some onions in ice-cube trays, so you can easily add just a bit of caramelized onions to something as you’re cooking. You’ll get a burst of flavor for almost no work.

Caramelized Onions 1200

Caramelized Onions in a Slow Cooker

Course: Condiment
Cuisine: French, American
Keyword: onions, component, slow cooker, crockpot
Prep Time: 15 minutes
Cook Time: 8 hours
Total Time: 8 hours 15 minutes
Servings: 8 cups
Use the slow cooker for a big batch of these onions
Print Recipe


  • ½ cup unsalted butter (1 stick)
  • 6 lbs large Spanish onions (about 6 onions)
  • 2-4 Tbsps fresh thyme


  • For 6 lbs of onions, I use a 6-quart oval slow cooker. If your cooker is smaller, use fewer onions.
  • Peel and cut the onions in half, then slice them about ¼” thick. Cut the butter into eight pieces and scatter them over the bottom of the slow cooker insert. 
  • Layer the sliced onions and fresh thyme leaves into the slow cooker. Don’t be afraid to completely fill the pot – they will cook down and not spill over.
  • Cover and cook on high for 2 hours. Stir the onions well, then replace the cover and cook on high at least 6 hours more, until the onions are tender.
  • When the onions are tender, if there is a lot of liquid in the pot, remove the lid and continue to cook on high another hour or so, until most of the liquid has evaporated.
  • Turn off the slow cooker and let the onions sit, uncovered, for an hour to cool.
  • Transfer to cup or pint jars and store in the refrigerator. 


NOTE: These onions freeze very well.