Preheat oven to 350 degrees. Grease 8 X 11 glass pan. Melt the butter in the pan in the oven. Remove carefully to heat proof surface.
Sprinkle graham cracker crumbs evenly over margarine and cover the entire bottom of the pan. Pour condensed milk evenly over graham cracker crumbs within 1 inch of sides of the pan.
Sprinkle chocolate chips evenly over the entire pan. Repeat with butterscotch chips and then walnuts. Sprinkle coconut evenly over the top if desired. Press firmly with back of fork.
Bake 20 to 25 minutes or until light golden brown. Cool completely and cut into squares. Store in a tightly covered container.