Beaumont began his career in show business in 1931 by performing in theaters, nightclubs, and radio. He began acting in motion pictures in 1940, appearing in over three dozen films. Many of those roles were bit parts and minor roles and were not credited. He often worked with the actor William Bendix. In 1946–47, Beaumont starred in five films as the private detective Michael Shayne, taking over the role from Lloyd Nolan. In 1950 he also narrated the short filmA Date with Your Family. From 1950 to 1953, Beaumont was the narrator of the Reed Hadley series Racket Squad, based on the cases of a fictional detective, Captain John Braddock, in San Francisco. In a 1953 episode of Adventures of Superman titled "The Big Squeeze", Beaumont played an ex-convict with a wife and son whose trust he must win back after an apparent return to his criminal past. In 1952, he played the role of Reverend Randy Roberts in an episode of The Lone Ranger. In Hadley's second series, The Public Defender, which aired on CBS in 1954 and 1955, Beaumont appeared three times in the role of Ed McGrath. Before Beaumont and Barbara Billingsley were cast as the parents on Leave It to Beaver, each had appeared separately in the early 1950s on Rod Cameron's syndicated detective series City Detective. Consistent with his interest in the clergy, Beaumont played the Reverend Clifton R. Pond in an episode of the religious anthology seriesCrossroads. He appeared in one of the early episodes of the CBS Western series My Friend Flicka and guest-starred in an episode of Frank Lovejoy's detective series Meet McGraw. In 1955, he also guest-starred in the Lassie episode "The Well", one of the first two episodes filmed as pilots for the new series. In those initial installments he portrays Mr. Saunders, a water company executive interested in purchasing the Miller family's well. In July 1957, Beaumont played a sympathetic characterization of the Western bandit Jesse James on the series Tales of Wells Fargo. Two months later, he was cast in his best-known role as the wise suburban father Ward Cleaver on the sitcomLeave It to Beaver. During that series' six seasons, Beaumont also wrote and directed several episodes, including the final one, "Family Scrapbook". In 2014, in recognition of his performances as head of the Cleaver household, TV Guide ranked Beaumont number 28 on its list of the "50 Greatest TV Dads of All Time". In 1959, just before Beaumont began filming the third season of Leave It to Beaver, he flew from his home in Minnesota to Hollywood while his wife, son, and mother-in-law traveled to California by car. A car accident killed his mother-in-law and severely injured his son. Jerry Mathers, the eponymous character of the show, later stated that the tragedy seriously affected Beaumont's participation in the production at the time, with Beaumont often just "walking" through his part. After Leave It to Beaver ended production and went into syndication in the fall of 1963, Beaumont appeared in many community theater productions and played a few guest roles on such television series as Mannix, The Virginian, Wagon Train, and Petticoat Junction. In February 1966, 11 years after his first appearance on Lassie, he again guest-starred on that popular series, performing in the episode "Cradle of the Deep". He also continued to have success as a writer, selling several television screenplays and radio scripts, as well as short stories to various magazines. Following his retirement from show business in the late 1960s, Beaumont launched a second career as a Christmas-tree farmer in Grand Rapids, Minnesota. He was forced to retire from that business in 1972 after suffering a stroke from which he never fully recovered.
Beaumont was married once. In Los Angeles on Easter Sunday, April 13, 1941, he wed actress Kathryn Adams at the Hollywood Congregational Church. Their union lasted 33 years, until their divorce in 1974. They had three children: Hunter, Kristy, and Mark. On May 14, 1982, Beaumont died of a heart attack while visiting his son, a psychologist working in Munich, in what was then West Germany. His body was cremated, and the ashes were scattered on the then family-owned island on Lake Wabana, Minnesota, near Grand Rapids. The 1983 telemovie Still the Beaver is dedicated to Beaumont.
