Grease an 8×8-inch square baking dish.

In a large pot over medium-low heat, combine 1/2 cup butter and 30 unwrapped caramels. Stir constantly until the caramels and butter are melted and the mixture is smooth.

Add 35 large marshmallows to the pot and continue stirring constantly until the marshmallows are fully melted and the mixture is smooth. Remove the pot from the heat.

Stir in 1/2 teaspoon vanilla and 1/4 teaspoon salt.

Add the dry ingredients to the pot: 4 cups multigrain Cheerios, 1/2 cup chopped salted roasted peanuts, 1/2 cup chopped banana chips, 1/2 cup chopped pretzel sticks, and 1/2 cup plain M&M’s. Using a sturdy spoon, mix until everything is evenly coated with the melted marshmallow-caramel mixture.

Pour the mixture into the greased 8×8-inch baking dish. Using buttered fingers or a buttered spatula, press the mixture evenly into the pan until compacted.

Let the bars cool at room temperature until set, then cut into squares and serve.