Returning to New Mexico, Marshall, in collaboration with his wife Nancy and the late Santa Fe Galloway, founded the New Playwrights Theatre in 1970 at the old Rodey Theatre on the UNM campus. The following year Marshall accepted the Chairmanship of the Department of Fine Arts and New Mexico Institute of Technology (NMIMT) where he taught Theatre Arts, Painting, Drawing and Film Aesthetics.

In the 1980's and 1990's Marshall worked in California and New Mexico in film and TV His Come Sweet Death, a short film inspired by J.S. Bach's musical composition, was awarded Outstanding Recognition at the Galveston on the Strand Film Festival. In addition his play, Eagle Boy was accepted into the permanent collection of the Langston Hughes Memorial Library in Los Angeles, California.

Marshall has four children and he and his wife Nancy reside in Bosque Farms, where he has his art studio.