She will play Barbara Fordham, the role she originated and for which she received Tony and Drama Desk nominations. She will be joined by the previously announced Phylicia Rashad, who begins performances the same day in the role of Violet Weston.
The show, which won the Tony Award for Best Play and the Pulitzer Prize for Drama, is directed by Anna D. Shapiro, who won the Tony for her work.
Morton previously appeared on Broadway in One Flew Over the Cuckoo's Nest, with other acting credits including Betrayal, Last of the Boys, The Well Appointed Room, Berlin Circle, The Royal Family, Homebody/Kabul, and Three Days of Rain.
August: Osage County currently stars Estelle Parsons as Violet Weston and Elizabeth Ashley as Mattie Fae Aiken, with Anne Berkowitz, Guy Boyd, John Cullum, Johanna Day, Kimberly Guerrero, Brian Kerwin, Mariann Mayberry, Michael Milligan, Sally Murphy, Troy West, and Frank Wood.