Sprinkle seasonings over turkey. Brush entire turkey breast with oil; place on a rack in a roasting pan
Insert meat thermometer in breast (do not touch bone). Bake at 325° for 2 1/2 hours or until thermometer registers 185°; baste with pan drippings.
Transfer turkey to a serving platter, reserving 1/2 cup pan drippings for Cream Gravy; let stand 15 minutes before carving. Serve with Cream Gravy. Garnish with watercress and mushrooms.