In this recipe, part of the homemade pie dough becomes the crust, and the rest, with the addition of oats and brown sugar, becomes the streusel topping. Keep the peels on the pears so they maintain their shape; the skins also give the pie a rustic quality. Bake the pie up to 2 days ahead, and serve at room temperature.
Lightly spoon 2 cups flour into dry measuring cups, and level with a knife. Combine 2 cups flour and 1/2 teaspoon salt in a food processor; pulse 2 times to combine. Add butter, and pulse 6 times or until the mixture resembles coarse meal. With processor on, slowly pour ice water through food chute, processing just until blended (do not allow dough to form a ball).
Remove two-thirds of dough, and press into a 4-inch circle on 2 overlapping sheets of plastic wrap. (Leave the remaining dough in processor.) Cover the dough with 2 additional sheets of overlapping plastic wrap. Roll dough, still covered, into an 11-inch circle. Place the dough in freezer 5 minutes or until plastic wrap can be easily removed.
Remove top sheets of plastic wrap, and fit dough, plastic wrap side up, into a 9-inch pie plate coated with cooking spray. Remove the remaining plastic wrap. Fold edges under; flute. Refrigerate until ready to use.
Add oats and brown sugar to dough in food processor; pulse 4 times or until crumbly. Cover and chill.
Preheat oven to 375°.
Combine pears, granulated sugar, 3 tablespoons flour, ginger, cinnamon, and 1/4 teaspoon salt; toss well to combine. Spoon pear mixture into crust. Bake at 375° for 25 minutes. Sprinkle oat mixture over pear mixture. Bake an additional 25 minutes or until top of pie is browned. Cool at least 2 hours.