Combine first 5 ingredients in a medium bowl; cut in margarine with a pastry blender until mixture resembles coarse meal. Add yogurt and peaches to flour mixture; stir just until dry ingredients are moistened.
Sprinkle 1 tablespoon flour evenly over work surface. Turn dough out onto floured surface, and knead lightly 4 or 5 times. (Dough may be slightly sticky.)
Pat dough into a 5-inch circle on a baking sheet coated with cooking spray. Cut circle into 4 wedges; separate wedges slightly. Brush milk over dough, and sprinkle with 1 teaspoon sugar. Bake at 400° for 14 to 15 minutes or until golden. Serve with peach spread, if desired.