In a bowl, combine sugar, cornstarch, lemon peel, cinnamon and nutmeg. Add apples and pineapple; toss to coat. Transfer to a greased shallow 2-quart baking dish.
In another bowl, combine oats, flour and brown sugar. Cut in butter until mixture resembles coarse crumbs. Stir in nuts; sprinkle over apple mixture. Bake, uncovered, at 375 for 30 minutes. Cover loosely with foil; bake 15 minutes longer or until apples are tender and topping is golden.