In Round 22 of the 1999 NRL season, he made his NRL debut for the Cowboys in their 8–40 loss to the Cronulla Sharks.[6] He played just one more game in his rookie season, spending the majority of the year playing for the Cairns Cyclones in the Queensland Cup.
In Round 13 of the 2000 NRL season, McWilliams scored his first NRL try in a 50–4 win over the St George Illawarra Dragons. That season he played 12 games for the Cowboys, starting eight in his preferred position of hooker. Over the next two seasons, McWilliams only featured sporadically for the Cowboys. In 2003, he started 14 games for the Cowboys at hooker before his season ended due to injury.[7][8] In 2004, McWilliams became a regular in the Cowboys side, playing 20 games as the club qualified for the finals for the first time.[9]
In 2005, McWilliams played just seven NRL games for the Cowboys, spending the majority of the season with the North Queensland Young Guns. On 17 September 2005, he started at lock in the Young Guns' 36–6 Queensland Cup Grand Final win over the Burleigh Bears.[10][11] He retired at the end of the 2005 season.[12]
Statistics
NRL
Statistics are correct to the end of the 2005 season[13]
^"Archived copy". www.cowboys.com.au. Archived from the original on 6 August 2001. Retrieved 12 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)