Oenslager was born in Harrisburg, Pennsylvania and attended Harvard University, graduating in 1923.
He had started as an actor in the 1920s at the Greenwich Village Theatre and the Harrisburg Playhouse.
He had received a Tony nomination two years earlier for his work on the play Major Barbara.
Oenslager's papers are held by the New York Public Library for the Performing Arts, although a number of his scenic design sketches are part of the permanent collection at the Museum of the City of New York.
[2] He brought "a new emphasis on symbolism over realism to American theater design.