Line a 9x9x2 inch pan with aluminum foil. (Leave about 1 inch hanging over the opposite sides so you can lift the bars easily from the pan.)
In a large bowl, mix the powdered sugar, margarine, 1 cup peanut butter, and vanilla. Stir in the cracker crumbs and peanuts. (The mixture will be stiff.) Press mixture into the pan.
Over low heat stir together the chocolate chips and 1/4 cup peanut butter until smooth. Spread over the mixture in the pan. Cover and refrigerate about an hour or until the chocolate is set. Remove from the pan and cut the bars into 36 squares. Refrigerate uncovered about 2 hours or until firm.
Cover and refrigerate any leftovers.