Cromer dropped out of high school in his junior year, later acquired a GED, and attended Columbia College Chicago.

[4] Cromer has been nominated for or won the Joseph Jefferson Award for his work in Chicago productions, winning for Angels in America Parts I and II in 1998, The Price in 2002, and The Cider House Rules in 2003.

[5][6] In 2005, Cromer made his Off-Broadway debut directing Austin Pendleton's Orson's Shadow at the Barrow Street Theatre.

[10] In 2009, Cromer performed the role of the Stage Manager in an Off-Broadway revival of Our Town, which he also directed, at The Barrow Street Theatre.

[13] In the wake of his Our Town success, The New York Times profiled Cromer, referring to "his suddenly thriving career [which] has etched him as a visionary wunderkind, a genius in a black cape with secrets up his billowing sleeves.

"[4] In October 2009, Cromer directed a short-lived Broadway revival of Brighton Beach Memoirs starring Noah Robbins, Santino Fontana, Laurie Metcalf, and Dennis Boutsikaris.

)[14] He directed the Broadway revival of The House of Blue Leaves, which starred Ben Stiller and Edie Falco and played a limited run from April 2011 to August 2011.

[21][22] In October to December 2013, he returned to Chicago to star as Ned Weeks in TimeLine Theatre Company's production of The Normal Heart by Larry Kramer.

[37] He was named a 2010 MacArthur Fellows Program, the foundation cited his efforts in reviving classic theater such as his work on The Adding Machine and Our Town in their announcement.