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.