Kate Valk is a founding member of the Wooster Group, a New York-based theatre collective started in 1974, and she has performed with the group for nearly four decades. Based at the Performing Garage at 33 Wooster Street, the group also performs at larger theaters such as the Baryshnikov Arts Center, St. Ann's Warehouse, and the Public Theater, and tours nationally and internationally. Wooster has become synonymous with productions that "subvert the text" and make use of elements such as video screens on stage, voice-overs, and a mixture of high and low cultural references. Valk's notable performances include Eugene O'Neill's The Emperor Jones (1993), playing Brutus with a blacked-up face and Kabuki gestures; House/Lights (1999), in which she recited the lines of Gertrude Stein's Faust as relayed to her via an earpiece in a mechanical Betty Boop-style voice, dressed as a 1930s vamp; and Hamlet (2006), in which the whole cast "channelled" the performances of actors in Richard Burton's 1964 film version, playing on screen behind the actors. Most recently, she played Mrs. Wire in the Wooster Group's production of Tennessee Williams' Vieux Carré, with performances in Europe, Canada, and Brazil.
Valk spoke to Philadelphia theater professionals in September 2007 about The Emperor Jones and other works made by the Wooster Group. In 2012, Theater magazine editor Tom Sellar interviewed her for the Center website.