Born and raised in Buffalo, New York, Greenbaum studied at the Massachusetts Institute of Technology (MIT) and the Sorbonne in Paris. Following service as a Navy pilot during World War II, Greenbaum moved to New York City to try his luck as a writer. He began work in radio as writer, producer and star of "Greenbaum's Gallery". He also wrote continuity for a radio series starring the Canadianfolk singerOscar Brand.[2][3]
In the mid 1950s, Greenbaum teamed with Jim Fritzell and collaborated on scripts for the TV series Mister Peepers (1952), a stylish sitcom starring Wally Cox as a timid small-town science teacher; it also gave Tony Randall his first important role. When the series was cancelled, NBC-TV received over 10,000 letters of protest. A month later Mr. Peepers returned, running for three years and winning a Peabody Award.[4]
In a 32-year partnership, Greenbaum and Fritzell also won three Writers' Guild awards and four Emmy nominations, and collaborated on more than 150 scripts. These included the Walter Brennan sitcom The Real McCoys (1957–62), The Andy Griffith Show (1960–68) and M*A*S*H, on which they worked for five years, contributing 35 episodes. On his own, Greenbaum wrote two books, including the memoir The Goldenberg Who Couldn't Dance, and 'The Tenth Life of Osiris Oaks' (with Wally Cox), and worked on The George Gobel Show. He also acted in brief roles on Mr. Peeper's (recurring), Griffith's Matlock (recurring), and series and other programs.[5][6]
Greenbaum died at the age of 79 in Los Angeles, California; he was survived by his wife Deane, and a daughter, Billie Shane (Greenbaum).[7] In a book published the year of Greenbaum's death, Don Knotts recalled of him, "Everett would come up with lines right out of the blue that would knock you off your seat. He also had an infectious cackle that was familiar to all his friends, and he had a multitude of friends."[8]