Prepare Lower-Fat Oil Pastry. On a lightly floured surface, flatten pastry. Roll into a 12-inch circle. Wrap pastry circle around the rolling pin; unroll pastry into a 10-inch tart pan with a removable bottom. Ease pastry into pan, being careful not to stretch pastry. press the pastry into fluted sides of tart pan and trim edges. Do not prick pastry.
For crumble topping, combine the oats, the 1/3 cup flour, the brown sugar, and the 1/2 teaspoon cinnamon. Stir in the butter or margarine. Set aside.
For filling, in a large bowl stir together the granulated sugar, the 2 tablespoons flour, and the 1 teaspoon cinnamon. Add the peaches and buttermilk. Gently toss until coated.
Spread filling evenly into pastry shell. Top with crumble topping. Bake in a 375 degree F oven 45 to 50 minutes, or until center of filling is bubbly. If necessary, to prevent overbrowning, cover loosely with foil the last 10 minutes of baking. Serve warm or at room temperature. Makes 10 servings.
Lower-Fat Oil Pastry
In a medium bowl stir together 1-1/4 cups all-purpose flour and 1/4 teaspoon salt. Combine 1/4 cup fat-free milk and 3 tablespoons cooking oil; add all at once to flour mixture. Stir with a fork until dough forms. If necessary, add 1 to 2 teaspoons additional milk. Shape the dough into a ball.