Prepare and preheat: Line a baking sheet with parchment paper. Preheat oven to 275°F.
Combine dry ingredients: In a large mixing bowl, combine 2 cups Rice Chex cereal, 2 cups mini pretzels, and 1 cup salted peanuts or cashews.
Cook caramel coating: In a small saucepan, add ½ cup butter and ½ cup brown sugar. Bring to a boil and cook on medium heat for 2 minutes. Stir in 1 teaspoon vanilla extract. Pour over Chex mix.
Bake: Bake for 15 to 20 minutes, stirring halfway through.
Add candy: Immediately add ½ cup M&M's, ½ cup candy corn or candy pumpkins, and stir.