Melt butter in a large saucepan coated with cooking spray over medium-low heat. Add marshmallows, stirring until melted. Add peanut butter, and cook until melted. Remove from heat.
Immediately add rice cereal; stir until cereal is coated. Press mixture into a 13 x 9-inch pan coated with cooking spray. Cool completely. Store in an airtight container.
Oxmoor House Healthy Eating Collection
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