O'Neill, who has signed a new one-year contract at Turf Moor, with an option for a further year, joins his hometown club after spending last season on loan in Australia with the Central Coast Mariners.
He said: “Last season I got to play in front of my family which was a big part of the decision for me to come to Australia on loan.
“To be back in my home city and be able to play in front of my family and friends means a lot to me.
“I'm really excited to get started in Brisbane. It's a great opportunity to play under Robbie, who had such an immense career.
“He called me and told me about his plans for the club and it was something I was really excited to be involved in."