Marshall was born in Oakland, CA, the firstborn of George William Elliott and Marive Margaret Elliott. He had a brother, Terry, and a sister, Valerie. Marshall and the rest of his family were born again when he was about 18. He spent 1 year at Cal Poly before attending and graduating from Western Baptist Bible College in El Cerrito, CA, where he met his wife, Norma. They were married in 1961, and had 4 children.

Marshall worked as a home missionary pastor under the Association of Baptist of World Evangelism, establishing Baptist churches in Nevada and California. He then moved to the Seattle area and took a job with Boeing Company, in charge of a portion of their aerodynamics program.

Marshall spent the remainder of his working years with Arrow Trucking. When he retired, he took up residence in Tulsa, OK, where he became a member of Tulsa Bible Church, teaching Sunday School almost until his death.