Second-half goals from Nikica Jelavic and Gregg Wylde - his first at Ibrox - secured the win after the opening 45 minutes had ended goalless.
The Scottish champions will now be hoping to open up a 10-point advantage over Celtic with victory over Hibernian on Saturday before their rivals are next in SPL action.
Rangers were forced to head into tonight's clash without Steven Naismith, who was yesterday handed a retrospective two-match ban for violent conduct during Saturday's win over Dunfermline.
Manager Ally McCoist made just one change for the visit of Killie, with Juan Manuel Ortiz drafted into the side in place of the suspended Naismith.
Kilmarnock had an early chance to open the scoring when James Fowler delivered a cross into the box for Paul Heffernan, who just failed to connect with the header in front of goal.
At the other end, Jelavic set up Sasa Papac for the shot and though he only had Cammy Bell to beat, the Killie goalkeeper was up to the task and did well to block the point-blank effort.
Jelavic had a decent chance of his own when the ball broke unexpectedly for him just inside the area but the Croatian striker connected awkwardly and the shot fell well wide of the upright.
Bell then bravely turned an Ortiz ball past the near post, with Jelavic loitering with intent in the goalmouth as the home side continued to press for the opener.
With half-time approaching, Maurice Edu tried his luck from distance but he was denied a repeat of his impressive strike at the weekend and watched as his effort dipped well over the crossbar on this occasion.
Gary Fisher picked up the first booking of the game shortly after the restart for a foul on Kyle Lafferty but Rangers failed to capitalise on the resultant free-kick, with Steven Davis' effort blocked by the wall and landing wide.
Fisher was followed into referee Willie Collum's book by Dean Shiels, for a foul on Wylde, before Bell threw himself in front of a Lafferty shot after the Northern Irishman was set up by Steven Whittaker for the best chance so far.
Fowler also earned himself a caution for felling Wylde and the foul proved costly when Jelavic met the free-kick from Davis and sidefooted home to open the scoring after 64 minutes.
Gary Harkins hit the crossbar for Kilmarnock but Rangers doubled their lead with 66 minutes gone when Wylde played a one-two with Edu before rifling into the back of the gaping net from six yards.
Rangers should have had the net bulging again when Jelavic turned provider for Davis but Bell just managed to palm the effort to safety and deny the midfielder the opportunity to add his name to the scoresheet.
Davis then returned the favour with a cross for Jelavic, who shrugged off Zdenek Kroca, only to blast over and fail to trouble Bell this time.
But, after a sluggish start to the match and clearly missing the influence of Naismith, Rangers were able to hold on for what was a comfortable win in the end.
