To prepare filling, combine first 4 ingredients in a medium bowl; set aside.
To prepare batter, place butter in an 8-inch square baking dish. Place dish in oven 5 minutes or until butter melts. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients (through dash of cinnamon) in a medium bowl. Combine milk and 1/2 teaspoon vanilla; add milk mixture to flour mixture, stirring just until moist. Spoon batter over butter, spreading evenly (do not stir). Spoon peach mixture over batter, gently pressing peaches into batter. Bake at 350° for 40 minutes. Sprinkle with turbinado sugar, and bake for an additional 10 minutes or until crust is golden.