Pursell was born in Oakland, California and raised in Tulare. He studied composition in Baltimore and arranged for the U.S. Air Force Band while serving in World War II. Bill Pursell studied classical composition under Howard Hanson at the Eastman School of Music and earned a master's in composition in the mid-fifties. His symphonic poem "Christ Looking Over Jerusalem" (the first movement of "Three Biblical Scenes for Orchestra") was the inaugural recipient of the Edward B. Benjamin Prize in 1953. Later that decade, he worked with the Nashville Symphony Orchestra and taught at Tennessee State University and Vanderbilt University.
In 1962 he signed with Columbia Records, who released a full-length album of his entitled Our Winter Love the following year. The album reached #15 on the Billboard 200 on the strength of the popularity of the title track, which hit #9 on the Billboard Hot 100 in addition to hitting #4 on the Adult Contemporary chart and #20 on the Black Singles chart. The arrangements for the album were made by Bill Justis and Pursell, and the orchestra was conducted by Grady Martin.
His follow-up single "Loved" reached Billboard position 121. Pursell later recorded for Epic, Henry Stone's Alston, and Dot, but never hit the pop charts again. He played piano on many of Johnny Cash's albums in the 1960s, and worked as a session musician and arranger for Patsy Cline, Johnny Paycheck, Hoover, Joan Baez, Eric Andersen, Scotty Moore, J.J. Cale, Willie Nelson, Dan Fogelberg, and others. In 1985, Pursell was named Composer of the Year by the Tennessee Music Teachers Association.