With a fine Scottish accent and unrivalled passing and control, McCallum is one of the Westfield most technically astute players ever to have worn the green and gold. Selected in the FIFA All-Star squad at the 2006 FIFA U-20 World Cup, McCallum has featured in 53 A-International matches scoring seven goals including several impressive free-kicks, most notably in the 2007 FIFA Women's World Cup. Since moving to Australia from her Scottish homeland, McCallum has been an integral member of Westfield Matildas, including appearances at the 2004 Australia's FIFA U19 Women's World Championships, the 2006 AFC Women's Asian Cup 2006, the 2006 FIFA U20 Women's World Championship 2006, the 2007 FIFA Women's World Cup 2007 and most recently Australia's historic win at the 2010 AFC Women's Asian Cup 2010. At club level McCallum has had successful stints in the USA and Australia including winning the WPS Championship in the USA with Sky Blues FC in New York.