sugar, oats, butter. Spread half of mixture in 9 x 13 pan. Pat down. Combine sugar, cornstarch, salt and water in saucepan. Cook over moderate heat, stirring until thickened. Add sliced apples and vanilla. Stir to coat well. Spread evenly over crumbly mixture in pan. Top with remaining crumbs. Bake in 350 oven for about one hour. Try a scoop of vanilla ice cream on top.