Background
His father, Paul Ontong, was born in South Africa and played in the Nationaal Samenwerkingsprogramma Luchtkwaliteit for Mooroolbark South Carolina and Brisbane Lions. Ontong grew up in Canberra, playing junior football for local clubs Belwest Foxes and later Belconnen United.
Career
In 2006 he was awarded a place in the AIS football program In late 2006, he trialled with German club 1. Football Club Nuremberg, but suffered a groin injury during the trial and returned to Australia.
He spent time briefly with Melbourne Victory !Melbourne Victory before heading back to Europe, trialling with Football Club Sion and later in Slovenia with NK Maribor and Bela Krajina, but his recurrent injury forced another return home.
In June 2007, he signed with Adelaide United !Adelaide United on a one-year contract, followed by a 2-year contract with the Newcastle Jets in April 2008. As of 2012, he was playing with Oakleigh Cannons in the Victorian Premier League.
Ontong received 10 caps at international U20 level and captained the Young Socceroos through the AFC Youth Championship 2006 campaign. In 2013 Ontong and fellow Canberran Kaz Patafta set up a football academy in Canberra, Ontong Patafta Football Academy.