After being overlooked for the Centenary Test against the Kiwis at the Sydney Cricket Ground in favour of Storm and Queensland fullback Billy Slater, and again representing NSW in the 2008 State of Origin series, Stewart was one of the form players for Manly in their run to the 2008 NRL Grand Final, and was the NRL's leading try scorer of the season with 22 tries from 24 appearances. In the Grand Final, Manly faced Melbourne for the second year running. 2008 would be very different to the previous season, however, as the Sea Eagles recorded the largest ever GF win of 40–0. While Stewart did not cross for a try in the GF, he provided the last pass on a couple of occasions for teammates to score, including the last try of the game for departing , Steven Bell.