Colleagues have included playwrights Samuel Beckett, Tennessee Williams, David Mamet, Richard Nelson, Spalding Gray, Wole Soyinka, Derek Walcott, John Guare, David Rabe, Edward Albee; countless leading actors, and directors including Peter Brook, Jerome Robbins, and Mike Nichols. Notable premiere productions include Six Degrees of Separation, John Leguizamo's Freak, David Rabe's Hurlyburly, Richard Nelson and Sean Davey's James Joyce's The Dead, the South African township musical Sarafina, and over twenty plays by Mr. Mamet, including American Buffalo, Speed-the-Plow, Edmond, and Glengarry Glen Ross. Recent work on Broadway includes plays by two Litchfield county writers, Love Letters by A.R. Gurney and A View from the Bridge by Arthur Miller.

In 2004, he was invited by Columbia president Lee C. Bollinger to create the Columbia University Arts Initiative, a program to foster student and faculty arts engagement across the university, which he led through 2010. In addition to providing wide access to NYC arts venues, and supporting student and faculty creative ventures, the Arts Initiative organized special events such a the month-long presentation of Peter Brook's Tierno Bokar, and the residency of the Czech playwright/president Vaclav Havel. Mr. Mosher currently teaches at Columbia's School of the Arts, where one of his classes is devoted to finding new producing models for the 21st century.