O’Malley won the Australian Junior Championship and the New Zealand Amateur Championship in 1986, and turned professional the following year.
He has won several times on the PGA Tour of Australasia, but spent most of the year playing on the European Tour. He was runner-up to Mark James in his first European Tour event, the 1989 Dubai Desert Classic, and has since won three titles on the European Tour.
Perhaps the most famous of these three victories was his Scottish Open win which he played the last five holes in seven under par to snatch victory. He made the top-100 on the European Tour Order of Merit every year from 1989 through to 2007, with a best ranking of tenth in 1995.
His greatest strength is his accuracy, and he topped the European Tour’s driving accuracy rankings in 2001 and 2002.