Later, she was featured for four seasons with the New York Shakespeare Festival Elizabethan Singers as one of a quartet consisting of Paula Janis (her eventual co-star on The Magic Garden) and their brothers, Jonathan Rosen and Alex Demas.

Demas' association with Tom Jones and Harvey Schmidt, creators of The Fantasticks (the longest running Off-Broadway show in theatre history), led to her participation in the workshop “Portfolio”.

Demas has guest-starred on many TV shows, among them Barnaby Jones, Kojak, Mannix, Fantastic Journey, The Man from Atlantis, and The Edge of Night; playing everything from victims to girlfriends to murderers.

Demas and co-star Paula Janis starred in the immensely popular and highly acclaimed children's TV program The Magic Garden, which was seen on WPIX-TV for over 12 years.

In addition to the three children's albums already completed (“Paula and Carole in the Magic Garden”, “Tales from the Storybox” and “Musical Goose on the Loose”), CAP Productions will release “Cottonmill Girls”, a collection of folk songs of the American textile mills, arranged and performed by Alex Demas.

In 2017, she set out with fellow Broadway star Sarah Rice (Sweeney Todd) to create a show honoring Tom Jones and Harvey Schmidt.

Demas' theater career began in 1963 as the ingenue lead (opposite Bert Convy and starring Patricia Neway) role in Morning Sun, an early Fred Ebb effort (before his partnership with John Kander).

She worked with writers Jim Jacobs and Warren Casey to develop the role,[4] which, in the original Chicago play (Grease Lightning) on which the musical was based, was considered too dark for the mainstream Broadway audience.

[5]: 182  The play, which was being produced in Los Angeles in preparation for a national tour prior to a Broadway opening, proved problematic from the start, and several efforts were made to fix it, including replacing Demas with Patti LuPone,[5]: 183  but to no avail.

[5]: 188 Her regional theatre credits include major roles in Barefoot in the Park (with Joan Bennet), Enter Laughing, Absence of a Cello (as Hans Conried's daughter), A Funny Thing Happened on the Way to the Forum as “Philia”, Oh, What a Lovely War, and her favorites,[citation needed] “Regina” in Another Part of the Forest at the Pennsylvania State Repertory Theatre, and “Angel” in Celebration at ACT in Seattle.

While working in Grease, Demas and long-time friend Paula Janis began starring in the television show The Magic Garden for WPIX-TV in New York City.

Demas has also appeared as a guest actor on many daytime and primetime series, including One Life to Live, The Edge of Night, Barnaby Jones, Mannix, Kojak, N.Y.P.D., The Man from Atlantis, and more recently Blue Bloods and Allegiance.

She has produced her one-woman show Summer Nights at the Laurie Beechman Theatre, and appears often in Broadway reviews, retrospectives, and fundraiser concerts: Demas currently resides in Westchester County, New York with her husband, Stuart Allyn.