1. Preheat oven to 475°. Stir together peaches, flour, nutmeg, and 3 cups sugar in a Dutch oven. Bring to a boil over medium heat; reduce heat to low, and simmer 10 minutes. Remove from heat; stir in butter and vanilla. Spoon half of mixture into a lightly greased 13- x 9-inch baking dish.
2. Unroll 2 piecrusts. Sprinkle 1/4 cup pecans and 2 Tbsp. sugar over 1 piecrust; top with other piecrust. Roll to a 14- x 10-inch rectangle. Trim sides to fit baking dish. Place pastry over peach mixture in dish.
3. Bake at 475° for 20 to 25 minutes or until lightly browned. Unroll remaining 2 piecrusts. Sprinkle 2 Tbsp. sugar and remaining 1/4 cup pecans over 1 piecrust; top with remaining piecrust. Roll into a 12-inch circle. Cut into 1-inch strips, using a fluted pastry wheel. Spoon remaining peach mixture over baked pastry. Arrange pastry strips over peach mixture; sprinkle with remaining 1 Tbsp. sugar. Bake 15 to 18 minutes or until lightly browned. Serve warm or cold with whipped cream.