Stephen is the co-author of the 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.
More recent theatre productions have included his surrealist thriller Drawer of Knives, and dystopian satire Intimacies. In 2015, his play Success, a comedy drama about the tangled relationships of three stand-up comedians, played in Auckland and Wellington.
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.