After graduating from Mt. Holyoke College in 1959, Ms. Vann—who was born Barbara Kutner in 1938 in Brooklyn—plunged into New York City's arts scene. She was a founding member, in 1962, of The Open Theater, which, under the direction of Joseph Chaikin, was one of the best-known and most successful avant-garde theatres of the day.

When the Open Theater dissolved in 1970, she and fellow Open Theater member James Barbosa founded Medicine Show. She ran the theatre continuously for 45 years.

Reviewing an early show (also called Medicine Show) by the company, the New York Times said the "company was formed by graduates of the Open Theater. If this show is an accurate indication of their art, the new group plans to accent openness. This is in all respects an amiable entertainment, so much so that one is easily willing to forgive the digressionary nature of the evening."

One production, Bound to Rise, based on the Horatio Alger story, won her an Obie for best direction.

Other Medicine Show productions included reworkings of Alfred Jarry's Ubu plays; her own adaptation for the stage of James Joyce's Finnegan's Wake; her new translation of Jean Genet's The Balcony; and her original vaudeville piece, Mr. Shakespeare and Mr. Porter, which weaved Cole Porter songs into Shakespearean tragedies. Ms. Vann also worked as a teacher, leading master classes at more than 80 universities throughout North America and on five European tours. She taught longer stints at Smith and Amherst Colleges and Yale and Colgate Universities.

She is survived by her daughter Regan and grandsons Thomas and John.