Pour dry pudding powder over ice cream and work into ice cream without letting ice cream melt. Add peanut butter and Cool Whip with fork. Add Grape Nuts. Pour into 8 x 8 pan and freeze. Cut into squares and serve.
Beth gave me this recipe years ago, and the family loves it. I have only used regular Cool Whip, but if you want to cut fat even further you could try fat free Cool Whip and the lower fat peanut butter and see how it turns out.