He made his professional debut opposite Michael Hurst in Theatre Corporate's 1985 production of Torch Song Trilogy.
[2] After founding the Auckland Theatre Company in 1992 and being its first Director from March 1992 – February 2003 he produced and / or directed over sixty mainbill productions including The Graduate, The Rocky Horror Show, Haruru Mai, The Daylight Atheist, Hair, Death of a Salesman, Wit, Art, Closer, The Judas Kiss, A Streetcar Named Desire and 12 Angry Men.
Prast was a co-star in the 1998 New Zealand movie, When Love Comes Along, with Rena Owen and Dean O'Gorman, directed by Garth Maxwell.
In 1988 he also performed on the Telethon, alongside EastEnders star Letitia Dean and Dalvanius Prime with the Pātea Māori Club.
[7] In 2009 Prast appeared as an arts commentator on TVNZ's Breakfast programme, sharply criticising the Auckland City Council for overspending on International Theatre Productions.
He gained recognition for his work as director of the inaugural Auckland Festival (2003), when it was voted by Metro Readers Poll as the "Event of the Year".