McCormick began acting in commercials at the age of 6 and, besides appearing in such classic sitcoms as "Bewitched", "My Three Sons" and "I Dream of Jeannie", provided the voice for the Chatty Cathy doll. She made her feature debut in Elia Kazan's "The Arrangement" (1969), starring Kirk Douglas and Faye Dunaway, but would not perform for the big screen again until "Pony Express Rider" (1976). Her best film work may have come as the high school girlfriend of Lorenzo Lamas in "Take Down" (1978), but it became increasingly difficult for her to get cast as anything but a teenager, despite her advancing years. After taking time away from the business to concentrate on building a family, McCormick returned to acting, starring as the wickedly funny and vampy Rizzo on Broadway and in touring company productions of "Grease" (1994-95).
After resuming her recording career with the country album "When You Get a Little Lonely" (1995), McCormick guest-starred on CBS's "Touched By an Angel" and NBC's "The Single Guy", for which the network, exploiting her Brady fame, promoted her "Marcia, Marcia, Marcia" episode into attracting the show's largest audience of the season. She established her revived TV career further with the role as the mother of a teenager in ABC's supernatural comedy "Teen Angel" (1997) and in the title role of "Get To the Heart: The Barbara Mandrell Story" (CBS, 1997). Back on top again, McCormick has her sights set on developing film and television projects that will stretch her talents on both sides of the camera and prove beyond a shadow of a doubt that there is indeed life after the Bradys.