In a medium bowl, mix together the butter or margarine, graham cracker crumbs, confectioners' sugar, and 1 cup peanut butter until well blended. Press evenly into the bottom of an ungreased 9x13 inch pan.
In a metal bowl over simmering water, or in the microwave, melt the chocolate chips with the peanut butter, stirring occasionally until smooth.
Spread over the prepared crust. Refrigerate for at least 2 hours and then let sit at room temp for 20 minutes before cutting into squares.