Cast of ER Cast of ER "ER" is an American drama series that aired on NBC from September 19, 1994 until April 2, 2009. The series featured a large ensemble cast that changed dramatically over its long run. The main cast was augmented by a wealth of recurring characters and award-winning guest stars. The original starring cast consisted of Anthony Edwards as Dr. Mark Greene, George Clooney as Dr. Douglas "Doug" Ross, Sherry Stringfield as Dr. Susan Lewis, Noah Wyle as medical student (later Dr.) John Carter, and Eriq La Salle as Dr. Peter Benton. Julianna Margulies guest starred in the pilot as
Cast of ER For Christmas." He took a job with a set schedule at another hospital in order to spend more time with his son, Reese, and his girlfriend, former fellow ER doctor Cleo Finch. La Salle returned for two more episodes in Season 8 and then again for two episodes in Season 15, including the series finale. Michael Michele's character, Cleo Finch, departed in the Season 8 episode "I'll Be Home For Christmas" with her boyfriend, and fellow doctor, Peter Benton, after having previously taken a job at the same hospital (in fact it was she who arranged the interview which resulted