Weerasinghe was educated at the Royal College Colombo and went on to study architecture at the University of Liverpool under Sir Patrick Abercrombie.
He gained wide recognition when he designed the "Lake House Building", the head office of the Associated Newspapers of Ceylon, owned by press baron D. R. Wijewardena.
During his tenure, he established four consulates and the Buddhist Temple of Washington, D.C. Oliver Weerasinghe married Christobel Kotelawala, the only daughter of Sir Henry Kotelawala, a member of the State Council of Ceylon from Uva and Badulla for 28 years.
Their son Rohan is a Senior Managing Partner of a major law firm and daughter, Menakka, is a former lecturer at the University of Michigan.
Weerasinghe died at Viharamahadevi Park, aged 72, after suffering a heart attack during a morning walk.