Step 1

In a medium bowl, use a fork to mix together oats, walnuts, brown sugar, flour, cinnamon and ginger. Drizzle with butter and combine to form a coarse crumb mixture. Set aside.

Step 2

In a large bowl, toss apples with sugar, lemon juice, cinnamon and ginger.

Step 3

Arrange apples in prepared pie crust. Sprinkle walnut streusel over top, completely covering the apples.

Step 4

Bake pie on a baking sheet, covered loosely with foil in center of a 375° F oven for 50 minutes. Remove foil and bake until streusel is golden and apples are tender, about 10 minutes more.

Step 5

Let sit 15 minutes before serving.