Combine first 4 ingredients in a Dutch oven, and let stand 10 minutes or until sugar dissolves. Bring peach mixture to a boil; reduce heat to low, and simmer 10 minutes or until tender. Remove from heat; add vanilla and butter, stirring until butter melts.
Unfold 2 piecrusts. Sprinkle 1/4 cup pecans and 2 tablespoons sugar evenly over 1 piecrust; top with other piecrust. Roll to a 12-inch circle, gently pressing pecans into pastry. Cut into 1 1/2-inch strips. Repeat with remaining piecrusts, pecans, and sugar.
Spoon half of peach mixture into a lightly greased 13- x 9-inch baking dish. Arrange half of pastry strips in a lattice design over top of peach mixture.
Bake at 475° for 20 to 25 minutes or until lightly browned. Spoon remaining peach mixture over baked pastry. Top with remaining pastry strips in a lattice design. Bake 15 to 18 more minutes. Serve warm or cold with vanilla ice cream.
*2 (20-ounce) packages frozen peaches may be substituted. Reduce sugar to 2 cups, flour to 3 tablespoons, and nutmeg to 1/4 teaspoon. Proceed as directed.
Note: To make ahead, let baked cobbler cool; cover and freeze up to 1 month. Thaw in refrigerator over-night. Uncover, and reheat in the oven at 250° for 45 minutes.