1. Line square pan, 9x9x2 inches, with aluminum foil, leaving 1 inch of foil overhanging on opposite sides.
2. Mix powdered sugar, margarine, 1 cup peanut butter and the vanilla in large bowl. Stir in cracker crumbs and peanuts (mixture will be stiff). Press in pan.
3. Heat chocolate chips and 1/4 cup peanut butter over low heat, stirring frequently, until smooth. Spread over crumb mixture. Cover and refrigerate about 1 hour or until chocolate is set.
4. Remove from pan, using foil to lift. Fold back foil; cut peanut butter mixture into 36 squares. Refrigerate uncovered about 2 hours or until firm. Cover and refrigerate any remaining squares.