1 (4 serving size) pkg. instant low-cal chocolate pudding
12 oz. ice cream (vanilla or chocolate)
1 c. Cool Whip
1/4 c. crunchy peanut butter
3 oz. Grape Nuts cereal

Combine all ingredients, except cereal, until evenly mixed. Stir in the cereal. Pour into 8 x 8 inch pan. Freeze.