The executive director will leave the theatre at the start of the 2018-19 season.
The director, designer, an arts leader will take on the leadership role in December.
Cooper joins Le Petit Theatre after leaving his position at American Conservatory Theater.
An experienced managing director, Bielstein succeeds Timothy Shields as leader of the resident theatre league.
The British-born director departs after six years leading the Kentucky theatre and its influential new-play program, the Humana Festival.
Until recently she served as marketing director and chief operating officer, and has roots in the company’s OSF days.
The former lawyer, now moving into arts management, joins the company’s new artistic director, Joanie Schultz.
Robinson will bring his experience with community development and social justice to the arts organization.
Herron, a California native, will join the company this fall as managing director.
Butkas and her family will relocate from Rochester, N.Y., to Massachusetts this fall.