The son of a career diplomat, he spent his childhood in Washington DC, Asia, and the middle east. Oliver graduated with a Bachelor of Arts degree with a major in Drama in 1983 from Tufts University. He then trained at Shakespeare & Co. with Kristine Linklater.


David E. Kelley originally wanted him to play the role of Bobby Donnell on the TV show "The Practice" (1997). Attended Tufts University. Has an older brother, Adam Platt and a younger brother, Nicholas Platt Jr. Was friends with "Huff" co-star Hank Azaria at Tufts University. He is also the paternal grandson of American architect Geoffrey Platt (by whom he has remote Dutch American ancestry) and wife Helen Choate. His mother, Sheila Maynard, was the daughter of Eileen Burden Maynard Robins (October 15, 1910 - March 24, 1970) and a granddaughter of the Hon. Cynthia Burke-Roche (October 4, 1884 - August 12, 1966), who married (1) Arthur Scott Burden (August 11, 1879 - June 15, 1921) in 1906, and (2) Guy Fairfax Cary Sr. (November 14, 1879 - August 27, 1950) in 1922. Cynthia was the sister of Edmund Maurice Burke-Roche, 4th Baron Fermoy in the Peerage of Ireland (of Irish and English extraction and son of the American heiress Frances Ellen Work), who was the maternal grandfather of Diana, Princess of Wales. His great-great-grandmother Frances Ellen Work's fortune was based on a maternal pork-packing fortune created in Chillicothe, Ohio, and a paternal dry good and finance fortune created in New York City. Her father Frank's fortune was estimated at $15 million, and he served as stockbroker to Commodore Vanderbilt. Brother of Adam Platt, New York Magazine restaurant critic.