The left back, 20, will be able to star for the Saints in the F.A. Cup after the Claret and Blue granted permssion for him to appear in the competition. Saints will be playing Bury in the fourth round and could enjoy a good run.
This will give the Northen Irishman a chance to showcase his talents on a national stage and possibly face Premiership opposition before he makes the step up with his parent club.
O'Halloran enjoyed a similar loan deal last season as he went to Wycombe and helped them to the semi-finals in the Carling Cup where they eventually lost to Chelsea.
The defender joins the growing list of Villa youngsters out on loan which includes players such as Isaiah Osbourne and Zoltan Stieber.
Another youngster out on loan can only be good news for Villa and good preparation for the player.