Barer began his career as a lyricist and songwriter in the late 1940s while working as a commercial artist/designer in New York. His most-heard song is the Mighty Mouse theme song.
He began by writing special material for supper club artistes like Celeste Holm and Dwight Fiske and then graduated to writing "pop" songs with Alec Wilder for such stars as Harry Belafonte, Sarah Vaughan, and Nat King Cole. He was later hired by Golden Records, for whom he wrote over 100 songs.
He had his greatest Broadway success came in 1959 with Once Upon a Mattress, for which he was lyricist and a book writer.
Barer began his own cabaret act in the 1970s, playing in clubs in Los Angeles and New York, where he would often reinterpret the lyrics of his own songs.
In 1972 he wrote 7 songs for Scarecrow in a Garden of Cucumbers a low-budget movie starring Holly Woodlawn.
Though a prolific writer, Marshall was largely unknown except to aficionados of "lost" musicals.
Popular Marshall Barer songs
- River Run
- La Ronde (This Is Quite a Perfect Night)
- Scratch My Back
- Roller Coaster Blues
- In a Little While
- Very Soft Shoes
- Song of Love (I'm In Love With A Girl Named Fred)
- Christmas long Ago
- What'll I Do With All the Love I Was Savin' for You?
- Warm Winter
- On Such A Night As This
- Walk Tall (1954)
- New Faces of 1956 (1956)
- Ziegfeld Follies (1957 starring Beatrice Lillie)
- Once upon a Mattress, with music by Mary Rodgers (1959) a comical rendering of the Hans Christian Andersen fairy-tale "The Princess and the Pea"
- Dancing on the Air (an adaptation of Shaw's The Devil's Disciple) with Dean Fuller
- Around the World in Eighty Days with music by Michel Legrand
- A Little Night Music (never produced)