2223 Technology Drive, Suite 35. O Fallon , MO 63368. Phone: (636) 561-5999. Fax: (636) 561-4746. Hours: Monday-Friday: 8 a.m. - 5 p.m. Schedule Appointment. You don't often think about your doctor until you get sick. Our team of family medicine specialists at Mercy Clinic Family Medicine - Winghaven wants to change that..