The 19-year-old Radcliffe earned rave reviews for his performance in the London production of the Tony-winning play. His portrayal of a disturbed teenager who blinds six horses requires him to strip down - a departure from his G-rated image as the boy wizard in the big-screen adaptations of J.K. Rowling's best-selling fantasy novels.
Radcliffe stars opposite Tony winner Richard Griffiths, who portrays his character's psychiatrist at Broadway's Broadhurst Theatre - as he did in London.
"The fact that he's willing to learn and risk is all to his credit," Turner said of Radcliffe.
Actress Lili Taylor said she was excited to see Radcliffe and Griffiths in the play, and doesn't consider the nudity to be any more shocking than it was it was when "Equus" debuted on Broadway in 1974.
"If it is, I think we have to grow up a little bit," she said.
Judith Light, Glenn Close, Dominic Cooper, Haley Joel Osment and James Lipton, host of Bravo's "Inside the Actor's Studio," also turned up at Thursday's event.
Cooper, now co-starring with Keira Knightley in the film "The Duchess," appeared with Griffith in the Tony-winning play "The History Boys" and its film adaptation.
"I dropped by (the theater) today and wrote some ridiculous scrappy little message to Richard in desperation for a ticket," Cooper said.