Matthew Garnaut played for local club Scarborough for 2 seasons before making his debut for Western Australia against South Australia in late November in the season of 1996-97. Garnaut made an inauspicious entrance to state cricket with 1 for 59 from 22 overs, and a golden duck but struck well in the South Australian 2nd innings with 4 for 81 from 27 overs which helped Western Australia win a very close game against the Redbacks.

During season 1998-99 Matthew Garnaut represented local club side Bayswater-Morley who made it through to the finals of the Smoke Free League and came up against Midland-Guildford. In that game suffering from a torn stomach muscle he rescued his team with a brilliant 127 not out in an inspiring 177 run 10th wicket partnership with team mate Brett Mulder which won Bayswater Morley the game and the competition. (Patrick Dean, August 1999)