Prior to acting, Gray began working as a model in the 1960s. Although the role was played by Anne Bancroft, Gray's legs were featured on the film poster of The Graduate (1967).
Gray began her professional acting career in the 1970s, with guest roles on series such as Marcus Welby, M.D. and McCloud. In 1978, she landed the role of Sue Ellen Ewing in the CBS series Dallas. Initially a recurring guest role for the five-episode first season, Gray became a series regular later in 1978 and remained with the show until 1989. She returned for the series finale in 1991 and also appeared in the Dallas reunion TV movies J.R. Returns (1996) and War of the Ewings (1998). Gray was nominated for an Emmy Award for her work on Dallas in 1981.