Mix apples, lemon juice, lemon peel, brown sugar and cinnamon together. Spoon into 8 x 8-inch greased, shallow baking dish. Set aside.
Mix butter, flour, brown sugar, cinnamon and nutmeg in medium bowl until mixture resembles coarse crumbs. Stir in walnuts. Sprinkle evenly over apples.
Bake at 375°F 35 to 40 minutes. Serve warm.