Peanut Butter Chocolate Bars

2 cups powdered sugar
2 cups graham cracker crumbs
1 cup creamy peanut butter
1/2 cup butter or margarine, MELTED
2 cups (about 12 oz.) chocolate chips (milk chocolate or semi-sweet)

Mix everything, EXCEPT chocolate, until blended. Spread into an ungreased 13x19 inch pan and press. Spread melted chocolate over the top. Refrigerate for 2 hours. Let stand at room temperature 15 to 20 minutes (take out before FHE starts) and cut into squares with a sharp knife.