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Grilled Cheese with Caramelized Onions and Three-Cheese Blend

Grilled Cheese with Caramelized Onions and Three-Cheese Blend

By Traeger Kitchen

Meet the grilled cheese to end all grilled cheeses. Sweet, caramelized onions and a three-cheese blend will make you wonder how you’ve lived without this sandwich in your life.

Prep Time

10 Min

Cook Time

1 Hr




This recipe serves:


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Units of Measurement:
As Needed Olive oil
Unsalted butter, softened, as needed
To Taste Salt
To Taste Pepper
2 Medium yellow onions, halved, and sliced 1/4-inch-thick
8 Slices White bread
As Needed Mayonnaise
As Needed Mustard
8 Slices fontina cheese
8 Slices mozzarella cheese
8 Slices white cheddar cheese


  • 1

    When ready to cook, set the Traeger temperature to 375˚F and preheat with the lid closed for 15 minutes.

    375 ˚F / 191 ˚C

  • 2

    Place a large cast iron pan on the grill grates and allow it to preheat for 10-15 minutes.

    375 ˚F / 191 ˚C


  • 3

    In the skillet on the grill, add a teaspoon of olive oil, and 1 1/2 teaspoons of butter to coat the bottom of the pan.

  • 4

    Add the onions, season with a pinch of salt and pepper and close lid. Cook for 40 minutes, stirring every 10 minutes, until the onions are a rich brown color.

    375 ˚F / 191 ˚C


  • 5

    Remove the onions from grill and increase the grill temp to 450˚F. Wipe out the skillet or use a cast iron griddle and place on the grill grates to preheat for 10-15 minutes.

    450 ˚F / 232 ˚C


  • 6

    For each sandwich, butter 2 slices of bread on one side, that will be touching the pan. Spread a thin layer of mustard and mayo on the other side of the bread slices.

  • 7

    Add 2 slices of each fontina, mozzarella, and cheddar cheese, then top with the caramelized onions.

  • 8

    Place your sandwiches in the preheated pan or on the griddle and close the lid. Grill for 8-10 minutes per side or until well browned and cheese is completely melted.

    450 ˚F / 232 ˚C


  • 9

    Remove from grill, slice in half into triangles and serve immediately. Enjoy!

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