FOR CRUST, combine 2 cups flour and powdered sugar. Cut in margarine until mixture is crumbly. Press onto bottom of 13x9 inch baking pan. Bake in 350'F. oven 15 minutes. Remove from oven. FOR TOPPING, combine drained pineapple, eggs, brown sugar and one third cup flour. Stir in pecans. Pour over partially baked crust. Bake in 350'F. oven 30-35 minutes or until set. Cool completely. Cut into bars. Makes 32 bars.