Robert Marion Cothran Jr. was born on May 9, 1930 to Minne Elizabeth and Robert Sr. in Detroit, Michigan. Cothran studied drama at Yale Drama School under Donald Oenslager. His career began as a stage designer in regional professional theater and educational theater. While work production assistant at Vanderbilt University, where he met his wife, Rosalyn. They married September 2, 1955 and had three children three children- David Branscomb, John Hardin and Ellen Elizabeth.

From 1972 to 1998, Cothran was the principle stage set designer and taught courses in set design, drawing, and scenic painting in the Theatre Department at the University of Tennessee, Knoxville. Cothran designed the sets for numerous plays at a variety of theaters, among them Knoxville’s own Clarence Brown Theater; most notably, The Merchant of Venice, The Tax Collector, and the revolving set for A Christmas Carol. In the 1980s, Cothran redesigned and updated sets for the Knoxville Community Nativity Pageant and continued to enhance it for the next twenty years. He also designed and painted settings for several opera productions for the Knoxville Rossini Festival, created set designs for the Alabama Shakespeare Festival and Milwaukee Repertory Theatre. Throughout his career, he has expressed himself through graphic design, printmaking, and mural painting. His lithographs are in the permanent collection of the Library of Congress, Smithsonian Institution, Ammon Carter Museum, UTK, and other public and private collections.

Cothran and his wife moved to Oberlin, Ohio in 2009 where he created an extensive three-part mural for the community of Kendal at Oberlin. In 2014, Cothran received the Clarence Brown Theatre Society Artistic Achievement Award. June 8, 2014 was also named as "Bob Cothran Day" by Knoxville Mayor Madeline Rogero for his achievements and legacy of craftsmanship, artistry, vision and for his dedication to the Clarence Brown Theater and the city of Knoxville, TN.