Coat 13-x-9-x-2-inch microwave-safe dish with vegetable cooking spray. Place six whole pieces of graham crackers in single layer in bottom; cut other pieces to fit remainder of bottom. Sprinkle marshmallows evenly over crackers. Microwave on high for one minute or until marshmallows are puffy; remove from microwave and cool completely.
In a 2-quart microwave-safe mixing bowl, combine chocolate morsels, corn syrup, and butter or margarine. Microwave on high for about 1 1/2 minutes or until chocolate can be stirred smooth. Stir in peanut butter. Add Rice Krispies and mix until evenly combined. Spread evenly over marshmallows. Cover and refrigerate about an hour or until firm. Cut into bars and store in an airtight container in refrigerator.
Yield: 36 squares or bars.