Melissa Leo has signed on to appear alongside Zachary Quinto in a benefit reading of Warren Leight play “Side Man” in East Hampton later this month.Leo and Quinto will be joined by five thesps, including Angelica Torn and Frank Wood, who appeared in the play’s original Broadway cast in 1998. Reading will benefit legit troupe Naked Angels, which was involved in the play’s early development. Quinto, who had an Off Broadway stint last season in the revival of “Angels in America,” plays the son of a struggling jazz musician played by Wood, who won a Tony for his perf. Leo has signed on as the musician’s alcoholic wife, a part played on Broadway by Edie Falco. The success of “Side Man,” which won the 1999 new play Tony, helped launch the career of playwright Leight, who became a busy TV scribe on skeins including “In Treatment,” “Lights Out” and two editions of “Law and Order.” The reading will take place Aug. 28 at East Hampton’s Guild Hall.