Born in Apia, Samoa in 1969, Oscar emigrated to New Zealand at age four. He grew up in Te Atatu in West Auckland, attending school there before leaving at the end of his 6th form year. He became a cadet reporter for the Auckland Star and later the Taranaki Herald (where fellow playwright Anthony McCarten also started a writing career).
Oscar spent four years working for the Auckland Star and the Sunday Star, covering everything from crime to sport to local body politics. In 1990 he worked for Independent Radio News before moving to Christchurch to work on TVNZ's teenage magazine Life 91.
Following the demise of that magazine, Oscar joined with actors in The Performing Arts Trust and later helped establish Pacific Underground, where Oscar's first co-written play Fresh Off The Boat was developed, presented and widely toured. Fresh Off The Boat, co-written with Simon Small, explores the lives and dilemmas of Samoan families living in New Zealand.
Following the success of Fresh Off The Boat, Pacific Underground set about touring further Pacific Island plays to schools. Oscar was instrumental in devising and co-writing these productions.
In 1996, A Frigate Bird Sings, co-written with David Fane, was an outstanding success at the 1996 International Festival of the Arts, playing at Downstage theatre in Wellington.
Oscar continued to work for Pacific Underground, performing also with Zeal Theatre in Auckland, devising work which toured to Sydney.
He has also worked extensively in television as a performer and a writer. His first solo venture as a playwright, Dawn Raids, premiered at the Herald in Auckland in 1997. In 1998 Oscar was awarded the Sunday Star Times Bruce Mason Playwriting Award.
In 2004, Oscar wrote Niu Sila with Dave Armstrong, which is still in professional production in New Zealand.

In 2006, Oscar co-wrote the New Zealand hit feature film Sione's Wedding with James Griffin.

Oscar currently works with the Naked Samoans on their TV3 series Bro' Town as well as making other regular appearances on television and radio.