Rangers lost ground on Celtic at the top of the Scottish Premier League, after they were held to a 1-1 draw by Aberdeen at Ibrox on Saturday.
The game had seemed to be heading for a stalemate.
Nikica Jelavic - linked with a host of English sides - had a header tipped on to the bar by Dons 'keeper Jason Brown, while Kari Arnason came close at the other end.
Arnason was celebrating in the 63rd minute, however.
Steven Davis lost the ball near the halfway line and Chris Clark led the break before feeding Arnason on the right.
The Swede then produced a fine finish to beat Allen McGregor, and he almost double their lead just minutes later from 30 yards. This time, McGregor saved.
Rangers equalised four minutes after Arnason's goal, Maurice Edu's shot getting deflected past Brown by an Aberdeen defender.
Edu almost grabbed a winner from Jelavic's cross, but the angle beat the midfielder.