O'Connor began competing internationally in the late 1970s, and in 1986 started riding with the US national eventing team, beginning with the Australian Gawler World Championships, mounted on Lutin V. She won multiple CCI3* events, including the Rolex Kentucky Three Day and the Fair Hill International, and the CCI4* at the 1999 Rolex event, riding Prince Panache. During the 1990s, O'Connor and her horse Biko were mainstays of the US eventing team, riding to multiple top-ten finishes at major international events, including the Badminton Horse Trials and the Rolex Kentucky Three Day. O'Connor rode at the 1994 World Equestrian Games and the 1998 World Equestrian Games, helping the US team to a bronze medal at the latter. At the 2006 World Equestrian Games she rode Upstage as an individual, but did not compete in the team portion of the event.