Preheat oven to 350 degrees. In large bowl, combine flour, 1/4 cup confectioners’ sugar, pecans and margarine. Press into bottom of 13-by-9-inch baking pan. Bake 20 minutes. Set aside to cool.
In mixing bowl, mix cream cheese and 2/3 cup confectioners’ sugar until creamy. Fold in 3/4 cup whipped topping. Spread cream cheese mixture over cooled crust.
In mixing bowl, beat sweet potatoes, sugar and cinnamon until smooth. Spread over cream cheese mixture. Top with remaining whipped topping. Refrigerate.