Stephen is the co-author of the 1987 comedy sensation Ladies Night, which continues to be performed throughout the world. In 2001, the French version won the prestigious Moliere Award for stage comedy of the year. Other plays include his historical drama The Bellbird, which was produced as a main bill for the Auckland Theatre Company in 2002 and was published by Reed in 2004. Reviewing it in the NZ Herald, Peter Calder called it “a play of heart and soul and a valuable addition to our literature.” In 2004, ATC premiered The Bach, a success they repeated in 2005. Both The Bellbird and The Bach are prescribed texts for Drama Studies in New Zealand secondary schools.
Stephen gained a BA in Māori studies in 1979 and worked as a researcher and subsequently translator of Māori transcripts for national archives. The tensions of race and culture are a common theme in his writing. He was active in the established Tao Tahi, a Pacific/Maori theatre company.
Stephen was co-writer on The Two Towers, the second film in The Lord of the Rings trilogy. Earlier collaborations with Peter Jackson and Fran Walsh include Meet the Feebles, and in 1991, Braindead, which won Best Screenplay at the 1993 New Zealand Film and Television Awards. In 2010, Stephen wrote and directed the feature Russian Snark, which went on to win numerous international awards.
He has written the novels Thief of Colours (Penguin Books, 1995) and Dread (Spineless Press, 2000). His collection of poetry, The Dwarf and the Stripper, appeared in 2003. Poems from the collection have been selected for two anthologies: Spirit Abroad: a Second Selection of Spiritual New Zealand Verse and 121 New Zealand Poems, selected by Bill Manhire.