Theatre Genesis was an off-off-Broadway theater founded in 1964 by Ralph Cook. Located in the historic St. Mark's Church in-the-Bowery in the East Village of Manhattan, it produced the work of new American playwrights, including Lanford Wilson, Tony Barsha, Murray Mednick, Leonard Melfi, Walter Hadler, and Sam Shepard. Theatre Genesis is often credited as one of the original off-off-Broadway theaters, along with Joe Cino's Caffe Cino, Ellen Stewart's La MaMa Experimental Theatre Club, and Judson Poets Theatre.

The theatre was known for its anarchistic, heterosexual, machismo energy, and often produced political plays. Like the other off-off-Broadway theatres, Theatre Genesis used a non-commercial model of production.

A young, progressive Episcopalian rector named Michael Allen came to St. Mark's in 1963 and opened the parish to everyone from the neighborhood. He did outreach to the many demographics and ethnicities in the East Village, which included artists, counterculturists, immigrants, and homeless people, among others. Allen aimed to fund arts and education initiatives in order to reflect the character of the neighborhood. Unlike Judson Church, in the West Village, the cultural programming at St. Mark's received minimal resistance from the church's older, wealthier, more conservative members.

Plays, poetry readings, underground films, and political gatherings began happening regularly at the church. Allen then decided an additional staff member was necessary to coordinate this programming, and hired Ralph Cook.

After temporarily employing the curator Tom Pike, Allen met Ralph Cook, an actor, who came to one of Allen's Sunday services. Cook began coming to the church regularly, and Allen and Cook became friends. Allen hired Cook for the role of curator, as Cook was well-connected in the downtown arts scene and had many friends who were looking for a space to showcase their creative work. His friends included Sam Shepard, Murray Mednick, Leonard Melfi, and Tom Sankey, among others. Their writing reflected the political and social upheaval that they were witnessing, and was often full of angst and testosterone. Their work didn't fit comfortably into the perceived camp aesthetic and looser structure at Caffe Cino and La MaMa. The church housed a 70-seat black box theater with sixteen lights, nine dimmers, spare sets, and minimal props. Much of the work being produced at the theatre had nihilistic themes. Cook said of Theatre Genesis:

As the theatre's newly-hired "lay minister of the arts", Cook began his routine of reading scripts. He quickly created a diligent and thorough selection process with a two-pronged production track: there was a season of six or fewer new plays, and a Monday night workshop series where playwrights could have their work read. Cook believed in giving new playwrights exposure and continuity, in order to develop the artist in addition to the individual play. Cook never commissioned work or guaranteed that a work would be produced in the future. While this often led Genesis playwrights to produce their work elsewhere, it also developed their trust in Cook to be honest and objective.

After an early off-key production of Michael Boyd's Study in Color, Cook produced a double-bill of one-acts by Sam Shepard. Cowboys and The Rock Garden were both homages to Samuel Beckett, and reflected Shepard's wanderings with then-comrade Charles Mingus III (son of Charles Mingus). The one-acts harnessed his youthful energy, using playful language, but also represented a raw, innovative voice from the streets. Shepard describes those first productions:

We were in rehearsal for [two plays] within that week... We had no money. I can remember getting props off the street. We'd take Yuban coffee cans, punch a hole in them, and use them for lights. We did it all from scratch, which was pretty incredible.