Heat oven to 350°F. Lightly grease 9-inch pie plate. In medium bowl, combine oats, flour, margarine and sugar; mix well. Press mixture firmly onto bottom and sides of pie plate. Bake 18 to 20 minutes or until golden brown. Cool completely on wire rack. Spoon frozen yogurt into cooled crust, spreading evenly. Cover and freeze 5 hours or until firm. Remove pie from freezer 10 to 15 minutes before serving. Cut into wedges. Top with fruit. Serve with topping, if desired. Store tightly covered in freezer.