Marchant was educated at Temple University in Philadelphia and the Yale School of Drama in New Haven, Connecticut.

Playwriting

Marchant's play, To Be Continued (which included a 23-year old Grace Kelly in the cast), opened on April 23, 1952 at the Booth Theatre on Broadway, and ran for 13 performances.

Marchant's most notable work, The Desk Set, opened on Broadway on October 24, 1955 at the Broadhurst Theatre and ran for 296 performances with Shirley Booth in the lead role. The play would serve as the source material for a 1957 movie of the same name starring Spencer Tracy and Katharine Hepburn.

He translated the French play Les Dames Du Jeudi for Lynn Redgrave and John Clark who premiered it as Thursday's Girls in Los Angeles in 1982.

In 1975, Marchant wrote The Pleasure of his Company, a remembrance of Noël Coward, which was published by The Bobbs-Merrill Company.

Screenwriting

As a screenwriter, Marchant wrote several episodes for the Armchair Theatre and Armchair Mystery Theatre, dramatized Louise, a W. Somerset Maugham story for a 1969 BBC Two television production, and worked on two films: Triple Cross and My Lover, My Son.