Slow Cooker Caramelized Onions

Yield Va on amount of onions used

Prep Time
10 minutes
    Cook Time
9 hours
Print Recipe      
1 fork recipe caramelized onions

Recipes are rated from 1 to 5 forks, with 1 fork being the easiest and 5 forks the most challenging.

Although this recipe takes all day, it is mostly hands-off once you slice the onions. This method produces a sweet and lightly browned version of caramelized onions. This is an absolute must if you enjoy onion soup or caramelized onions in any dish.

Instructional images follow the recipe.


  • 3 large Sweet yellow onions (or as many as your slow cooker will hold)
  • 1/4 cup water
  • 1 teaspoon fresh thyme leaves (+ 1 tsp if you use more than 3 onions)
  • 1 stalk Celery - finely diced

Special Equipment:

  • Slow Cooker (crockpot)   (like this one)    

    Preparation Method:


    The method of slicing the onion is important. Cut the onion in half from the root end to the tip. When slicing the onion into half-moons, slice the onion from the root to the tip as illustrated in the images below. The grain of the onion runs from the root to the tip, and this method will help keep the onion slices from disintegrating into small pieces when cooked for an extended period of time.

    The celery acts as salt for those on a low-sodium, and will help bring out the sweetness in the onions.

    Cutting the onions:

    Slice the top and bottom from each onion and peel off the skin. Slice the onion in half from root to tip. Lay each half onion cut side down and slice into 1/4 inch half-moons from the root end to the tip.

    Cooking the onions:

    Place the sliced onions in the crockpot container and sprinkle with thyme leaves and diced celery and pour the water over the onions. Cover with the crockpot lid and turn the crockpot onto high heat for 1 hour. Stir the onions after 1 hour and turn the heat down to low. Cook the onions for an additional 7 to 8 hours, stirring occasionally if possible.

    The onions will be soft and sweet, but will not be dark brown. At this point, you can use the onions as they are, you can refrigerate the onions in a sealed container for up to 4 days, or you can freeze the onions in a sealed bag for up to 3 months.

    If you would like darker, more caramelized onions, you can finish them in a non-stick pan over medium-high heat for 2 to 4 minutes, or until the desired brown color has been achieved.

    Preparing and cooking the onions:

    For onions that will not fall apart when cooking long and slow, you should slice them from the root to the tip as described in the instructions.

    {image: slicing onion}

    Place the onions in the crockpot and add the celery (or salt) and thyme. Pour in the water and stir before beginning to cook.

    {image: Add celery and herbs}

    Onions in the crockpot after about 6 hours, time to stir!

    {image: caramelize onions in crockpot}

    Onions after 9 hours and finished in a non-stick pan for about 2 minutes

    {image: caramelized onions}