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How to Caramelize Onions in a Slow Cooker

The easiest way to make caramelized onions, in a slow cooker
Prep Time10 mins
Cook Time12 hrs
Total Time12 hrs 10 mins
Course: Condiment, Sauce
Cuisine: American
Keyword: caramelized onions, onions
Servings: 3 cups


  • Slow Cooker


  • 3 pounds yellow onions sliced thin, about 4 each
  • 2 tablespoons extra virgin olive oil
  • 2 teaspoons kosher salt
  • ½ teaspoon black pepper freshly ground


  • Peel the onions and cut them in half. Thinly slice them crosswise.
  • Place the sliced onions in a bowl and toss them with the olive oil, salt, and pepper.
  • Place the onions in the slow cooker, turned on low. Cook for 4-5 hours and then check and give them a stir. You can also put them in when you go to bed and let them cook overnight. They will take 10-12 hours to get to the caramelized (sweet and brown) stage.
    Caramelized Onions in Slow Cooker After 4 hours
  • If after 10-12 hours, they have too much liquid in the bottom of the pot, let them cook for 30 minutes to an hour with the lid ajar so that some of the moisture evaporates.
    Caramelized Onions in the Slow Cooker When Done
  • When the onions are done, cool and refrigerate or freeze. See notes on freezing below.
    Caramelized Onions in Souper Cubes for Freezing


Caramelized onions should keep for up to 14 days in the refrigerator or up to 6 months in the freezer.
I highly recommend Souper Cubes for freezing sauces, soups, and yes, even caramelized onions. I froze them and then popped them out, wrapped them in plastic, and packaged them up for later use.
Caramelized Onions packaged for the freezer
Caramelized Onions packaged for the freezer (yes, I know they are spelled wrong!)