O.L. Duke's acting career breakthrough occurred when he replaced Denzel Washington in Charles Fuller 's Pulitzer Prize-winning original production of "A Soldier's Play" (later made into the film A Soldier's Story (1984). He was a member of both the renowned Actors Studio and the Negro Ensemble Company (NEC). He appeared in numerous off-Broadway plays and on other well-known stages throughout the US and abroad, including The Kennedy Center and Ford Theater in Washington, D.C.; Connecticut's Hartford Stage and The Long Wharf Theater; The Geva in Rochester, New York; The Guthrie in Minnesota; The Cincinnati Playhouse in the Park, The ACT Theater in Seattle, Washington; and The Royal Lyceum Theater in Edinburgh, Scotland. Duke guest-starred and co-starred in award-winning television productions, such as Homicide: Life on the Street (1993), NYPD Blue (1993), Law & Order (1990), New York Undercover (1994), HBO's original series Oz (1997), and the PBS documentary _"This Far by Faith" (2003) (mini)_. Some of his theatrical film credits include Out of Time (2003), Antwone Fisher (2002), Piñero (2001), The Keeper (1995), Sugar Hill (1993), Malcolm X (1992) and The Five Heartbeats (1991).