Preheat oven to 350 F. IN a large bowl, combine the first four ingredients. Cut in butter until crumbly. Press half of mixture into a greased 2 1/2 qt. baking dish or a 9 inch square baking pan. Cover with apples.
In a small saucepan, combine the sugar, cornstarch, water and vanilla. Bring to a boil; cook and stir two minutes or until thick and clear. Pour over apples. Sprinkle with remaining crumble mixture.
Bake 60-65 minutes or until apples are tender. Serve warm, with ice cream if desired.