Place popcorn in a large bowl; set aside. In a large saucepan, combine the butter, corn syrup and candies; bring to a boil over medium heat, stirring constantly. Boil for 5 minutes, stirring occasionally. Pour over popcorn and toss to coat. Transfer to two greased 15-inch by 10-inch by 1-inch baking pans. Bake at 250° for 1 hour, stirring every 15 minutes. Remove from pans and place on waxed paper to cool. Break apart; store in airtight containers.