Originally from Beaufort via North Ballarat under-18s, O'Bree was the nephew of former Collingwood and Richmond forward Allan Edwards, whose father Arthur played with Footscray. He was also related to Dick O'Bree who had a brief career at Collingwood in the 1950s.

As a teenager he was considered one of the hottest properties around and was thought unlucky not to be picked up in the 1996 National Draft as a 17 year-old.

Drafted to Brisbane, he had a limited taste of AFL football in 1998 as a forward pocket and half-forward flanker and in 1999 began the season well as part of a mean Brisbane defence

The Lions had long-term ideas of grooming him as a midfielder, and though he played capably in two finals in his second season on the list, he expressed his desire to return home to Victoria because he could not come to terms with the Lions, and Collingwood picked him with the No.1 selection in the December 1999 pre-season draft.

Collingwood coach Mick Malthouse had been keen on drafting him when Malthouse was at West Coast.

O'Bree settled smoothly into the Magpies' line-up and not only was an ever-present in the team in 2000, but proved himself one of the most important members of the team.

O'Bree finished fifth in Collingwood's best and fairest in his first season and started 2001 in slashing form and constantly pumped the ball out of the middle for the Magpies to finish fourth in the best and fairest. He became a constant force for the Magpies for most of the next decade.

He was slow to start in 2002 because of osteitis pubis, but he eventually reclaimed his position, playing in the losing Grand Final sides of 2002 and 2003.

O'Bree had an unspectacular 2004 season punctuated by a knee problem that sidelined him for four weeks and he needed to quickly turn the trend around.

He had an excellent 2005 and continued to be a stalwart through to the end of 2009.

In 2010 he was supplanted by younger midfielders and with just six senior appearances drew the curtain on a fine career.