As a young man Burr weighed more than 300 lbs., which limited his on-screen roles. "But in radio this presented no problems, given the magnificent quality of his voice," reported The Globe and Mail. "He played romantic leads and menacing villains with equal authority, and he earned a steady and comfortable income." Working steadily in radio since the 1940s, often uncredited, Burr was a leading player on the West Coast. He had a regular role in Jack Webb's first radio show, Pat Novak for Hire (1949), and in Dragnet (1949-50) he played Joe Friday's boss, Ed Backstrand, chief of detectives. Burr worked on other Los Angeles-based series including Suspense, Screen Directors Playhouse, Yours Truly, Johnny Dollar, Family Theater, Hallmark Playhouse and Hallmark Hall of Fame. He performed in five episodes of the experimental dramatic radio anthology series CBS Radio Workshop, and had what is arguably his best radio role in "The Silent Witness" (1957), in which his is the only voice. In 1956 Burr was the star of CBS Radio's Fort Laramie, an adult Western drama produced, written and directed by the creators of Gunsmoke. He played the role of Lee Quince, captain of the cavalry, in the series set at a post-Civil War military post where disease, boredom, the elements and the uncharted terrain were the greatest enemies of "ordinary men who lived in extraordinary times". The half-hour transcribed program aired Sundays at 5:30 p.m. ET January 22 - October 28, 1956. Burr told columnist Sheilah Graham that he had received 1,500 fan letters after the first broadcasts, and he continued to receive letters praising the show's authenticity and presentation of human dignity. In August 1956, CBS announced that Burr would star in the television series Perry Mason. Although the network wanted Burr to continue work on Fort Laramie as well, the TV series required an extraordinary commitment and the radio show ended. Known for his loyalty and consciousness of history, Burr went out of his way to employ his radio colleagues in his television programs. Some 180 radio celebrities appeared on Perry Mason during the first season alone.

Answer this question "what did he do on the radio" by extracting the answer from the text above.
He played romantic leads and menacing villains with equal authority, and he earned a steady and comfortable income."