Line an 8-inch square baking pan with foil, extending foil over edge of pan. Coat with no-stick cooking spray.
Melt butter in a large saucepan (4 qt.) over low heat until melted. Add marshmallows stirring until completely melted. Remove from heat. Blend in 1 1/4 cups peanut butter chocolate spread mixing until combined. Add cereal. Stir until well coated. Press into prepared pan. Cool completely.
Frost treats with remaining peanut butter chocolate spread. Remove treats from pan using edges of foil. Cut into 32 bars.