Newman began her comedy career as a member of The Groundlings and is most well known for being an original cast member on NBC's Saturday Night Live, appearing on the show from its inception in 1975 through 1980.

Newman's film career has been limited, having been hampered from the start by tepid critical and commercial response to her first leading role, supporting Dudley Moore in 1980's cameo-laden biblical satire Wholly Moses.

She has achieved greater success in supporting roles and as a voice artist on television, including appearances on such programs Laverne & Shirley, St. Elsewhere, Amazing Stories, Friends, The Tick, 3rd Rock from the Sun, Curb Your Enthusiasm, As Told By Ginger, and Rugrats (in "All Growed Up," an episode which would form the basis of the spinoff All Grown Up!, for which she also provided voice work).

In 1993, Newman appeared in the Coneheads, a full length motion picture based on the Saturday Night Live sketch of the same name. On television, she played The Coneheads' daughter, Connie; in the movie, she appeared briefly as "Laarta Conehead", an adult relative of the alien family. Other films include The Flintstones (1993) and voice work in Monsters, Inc. (2001).