Line a 9-inch square pan with greased foil or parchment paper.

In a large pot set over medium low heat, melt butter, peanut butter, and 8 cups of the mini marshmallows, stirring frequently.

Once completely melted, add crispy rice cereal, whole grain oats cereal, and oats and stir until combined.

Add the remaining 2 cups mini marshmallows, mini chocolate chips, mini M&Ms, and chopped peanuts and gently stir until incorporated.

Immediately dump into the prepared pan. Use a greased spatula or fingers to gently press mixture evenly into the pan, careful to too compact it too tightly. Sprinkle with additional mini chocolate chips, M&Ms, peanuts, etc. if desired.

Let sit for 30 minutes (or in the fridge for 10 minutes), then slice and serve. Store in an airtight container.