Spray a 9X13 pan with a non-stick cooking spray and set aside.
Add 6 tablespoons butter and 2 packages marshmallows to a large saucepan.
Once the ingredients are melted and combined, remove the saucepan from the heat and gradually stir in 10 cups Rice Krispie cereal until evenly coated.
Gently fold in 2 cups red and green M&Ms and 2 tablespoons Christmas sprinkles, reserving some for topping.
Press the mixture into the 9X13 pan. I spray a piece of parchment paper with non-stick spray and use that parchment paper to press the cereal down into the baking dish.
Then top with the reserved M&Ms and sprinkles. Gently press these down so that they stick into the Rice Krispie treats.
Let the Rice Krispie treats sit at room temperature for 1 hour and then they are ready to slice, serve and enjoy!
Notes
Store any leftover Rice Krispie treats in an airtight container at room temperature for up to 1 week. Do not store these treats in the refrigerator. They are best left to cool at room temperature so that they remain gooey and delicious!