Combine butter, graham cracker crumbs, powdered sugar and peanut butter in medium bowl. When well combined, pat into a well greased 8 x 8 inch pan. Refrigerate while preparing topping.

Melt chocolate chips and oil together in microwave, stirring every 30 seconds or so, till smooth. Spread over top of peanut butter layer.

Refrigerate at least an hour before cutting.