Cut butter into flour with a pastry blender or fork until mixture resembles coarse meal. Stir in pecans. Press mixture onto bottom of a 9 x 13" pan. Bake at 350°F for 15 minutes or until lightly browned. Cool.
Beat cream cheese, powdered sugar, and 1 cup of the Cool Whip at medium speed with an electric mixer until smooth. Spread mixture over cooled crust.
Whisk together instant pudding mix and milk 2 minutes, or until smooth. Spread over cream cheese mixture. Chill 10 minutes. Spread remaining whipped topping over pudding mixture. Cover and chill at least 1 hour.