Spray pan thoroughly with pan with vegetable pan spray.
In large bowl, microwave butter for 1 minute to melt. Add marshmallows and peanut butter and stir to coat. Microwave for 1 minute. Stir. Microwave for 1 more minute to fully melt. Stir until well combined. Add cereal, raisins, and peanuts to the bowl. Mix well until everything is evenly coated.
Pour mixture into pan. With the back of a spatula, press mixture firmly into the pan. Allow to cool to room temperature before inverting onto a serving plate.
Makes about 12 servings.