After one season with London Irish, McCusker returned to Wales, signing for the Ospreys as injury cover for Sam Underhill.
McCusker was initially named by Wales coach Warren Gatland on a 50-man list of potential 2011 World Cup players.
He was named in the Wales squad to play against South Africa, New Zealand and Australia in Summer 2010 after being promoted from the standby list due to injury to Andy Powell.
[6] On 26 June 2010, McCusker impressed after replacing number eight and Wales captain Ryan Jones in the 25th minute of the second Test in Hamilton against the All-Blacks.
[9] McCusker was not selected for the squad for the 2012 Six Nations, but returned to the side for the 2012 end-of-year rugby union internationals, coming off the bench against Argentina.