O'Neill, who made two appearances for the Clarets last season against Plymouth in the Capital One Cup and then as a sub in the last game of the season against Ipswich, has been on and off the bench so far this season.
He was a summer 2012 signing by previous manager Eddie Howe from Mansfield and will now go out to get some football over the next four weeks and will go into York's squad for their game at Torquay tomorrow.
He knows all about his new temporary club; his last two appearances for Mansfield came against them in the Conference play-off semi-finals with York going on to win 2-1 on aggregate before beating Luton in the final to regain league status.
He'll be with York until 31st October during which time they will play six games.
Source: Clarets Mad