Cut squash in half lengthwise; discard seeds. Cut each half widthwise into 1/2-in. slices; discard ends. Place slices in an ungreased 13-in. x 9-in. baking dish. Sprinkle with garlic and drizzle with 1 tablespoon oil.
In a large skillet, brown chicken in remaining oil. Arrange chicken over squash. Combine the brown sugar, rosemary and salt; sprinkle over chicken. Bake, uncovered, at 350° for 45 minutes, basting with pan juices twice.
Pour peaches over chicken and squash. Bake, uncovered, 15 minutes longer or until a thermometer reads 180°.Yield: 4 servings.