Combine oats, 1 cup flour, and sugar in a large bowl. Cut in margarine with a pastry blender until mixture resembles coarse meal. Press one-half of oat mixture into bottom of a 9-inch square pan coated with cooking spray. Bake at 350° for 15 minutes. Remove from oven; sprinkle walnuts over prepared crust.
Combine syrup and remaining 1/4 cup flour; stir well. Pour syrup mixture over nuts. Sprinkle remaining oat mixture over syrup mixture. Bake at 350° 25 to 30 minutes or until golden. Let cool in pan on a wire rack. Cover and chill at least 1 hour. Cut into bars.