In a large bowl, combine the first five ingredients; set aside. In a heavy saucepan over low heat, melt butter and 2/3 cup butterscotch chips. Remove from the heat. Stir in the dry ingredients and egg until well blended.
Spread into an ungreased 15x10x1-in. baking pan. Sprinkle with peanuts and remaining chips. Bake at 300° for 25-30 minutes or until lightly browned.
Immediately cut into bars and remove from pan. Cool on wire racks. Store in an airtight container.