Discharged in 1946, Brady headed to Los Angeles, California. where his older brother Lawrence was already making some progress as an actor. First taking menial jobs as a cab driver and a lumberjack, Brady enrolled at the Bliss-Hayden drama school under his G.I. Bill of Rights. There he studied acting and did vocal training to eliminate his thick Brooklyn accent.

From 1953 to 1956, Brady appeared four times in different roles on the anthology series, Lux Video Theatre. In 1955, he portrayed Ted Slater in "Man in the Ring" of NBC's anthology series, The Loretta Young Show. From 1953 to 1956, he appeared five times on the NBC anthology series, The Ford Television Theatre. In 1955 and 1957, Brady was twice cast on another anthology program, Studio 57. Early in 1957, he was cast in "The Barbed Wire Preacher" of the religion anthology series, Crossroads.

From 1955 to 1959, Brady appeared five times on CBS's anthology series Schlitz Playhouse, including as the roles of Reno Cromwell in "Night of the Big Swamp" and Calvin Penny in "Papa Said No." The Schlitz Playhouse episode "The Salted Mine" became the pilot for Brady's own western television series, Shotgun Slade, which aired seventy-eight episodes in syndication from 1959 to 1961.

On December 26, 1957, he played the frontier figure william Bent in the episode "Lone Woman" of CBS's anthology, Playhouse 90, with Raymond Burr cast as his brother, Charles Bent. The plot involved the establishment in Bent's Old Fort on the Arkansas River in southeastern Colorado. Kathryn Grayson played the "Lone Woman," a Cheyenne Indian.

In 1958, he played the lead role of Sergeant Matt Blake to Clint Eastwood's third billing as Keith Williams in Ambush at Cimarron Pass, a film which Eastwood is quoted as having called "probably the lousiest western ever made." This film is also notable for a scene in which Brady beats Eastwood in a fistfight, possibly the only screen-fight that Eastwood ever lost.

In 1961, he played the roles of John Keller in "We're Holding Your Son" on the anthology series hosted by Ronald W. Reagan, General Electric Theater, and Ernie Taggart in "Voyage into Fear" of the CBS detective series, Checkmate. In 1962, Brady was cast in the lead guest role as reporter/commentator Floyd Gibbons in "The Floyd Gibbons Story" of ABC's The Untouchables, starring Robert Stack. The next year he portrayed Bill Floyd in the episode "Run for Doom" of CBS's The Alfred Hitchcock Hour. In 1967, Brady guest starred on Carl Betz's ABC legal drama, Judd, for the Defense. In 1969, he portrayed Budd Blake in the episode "Panic" of the NBC drama Bracken's World. In 1973, he was cast as Davey Collier in "No Stone Unturned" of NBC's Banacek. From 1975 to 1977, Brady had the recurring role of "Vinnie" in sixteen episodes of NBC's Police Story crime drama.

In 1963, he was barred by the New York State Harness Racing Commission from participation in the sport due to his association with known bookmakers.

On February 15, 1977, he appeared as Shirley Feeney's father, Jack Feeney, in the episode "Buddy, Can You Spare a Father?" on ABC's Laverne & Shirley. Though he had turned down the role of Archie Bunker on All in the Family, Brady appeared as Joe Foley on four episodes in 1976. He appeared five times on the James Garner NBC series, The Rockford Files. In 1977, he portrayed Lou Caruso in "Caruso's Way" of ABC's sitcom Welcome Back, Kotter, and appeared as Matt Zaleski in the TV miniseries Wheels the following year.

In 1981, Brady was stricken with pulmonary fibrosis and thereafter required the use of an oxygen tank. He died four years later at the age of sixty. He is interred at Holy Cross Cemetery in Culver City, California.

In 1983, Brady portrayed Alex Kidd in "Shadow of Sam Penny" on the CBS detective series Simon and Simon. Brady's last film acting role was as Sheriff Frank in the 1984 film Gremlins.