Heat oven to 375°F.
In bowl, mix flour, sugar, cinnamon and ginger. Add butter; work into flour mixture with fingers until coarse crumbs form. Stir in walnuts. Gather mixture together.
Peel apples. Halve; core. Cut into 1/4- to 1/8-inch-thick slices. Place in large bowl. Add sugar, cornstarch, ginger and cinnamon; toss to coat apple slices.
Coat 2-1/2-quart baking dish with nonstick cooking spray. Spoon apple mixture into dish. Break topping into large crumb pieces; sprinkle over filling. Cover dish with foil.
Bake in 375°F oven for 30 minutes. Uncover dish. Bake 25 minutes or until top is crisp and browned and filling is thickened and bubbly. Let cool 15 minutes before serving.
