The veteran has signed a two year deal with the Australian club.
Dorrans has played more than 400 professional games in his career.
He will arrive and join up with the squad after following COVID-19 quarantine procedures.
"I'm delighted to be coming over and grateful for the opportunity to play for the club," said Dorrans, per the club website.
"After speaking with the manager (Carl Robinson) and hearing the vision he has for the club and the way he wants to play I think it's a brand of football that really suits my game.
"It's a league I have watched from a distance and really enjoyed watching it so I'm looking forward to getting over and starting as soon as I can."