Nacho Novo’s fourth-minute goal was enough to separate the sides but, in truth, for the second match in succession Walter Smith’s side put in a sub-standard performance against opposition languishing in the bottom half of the table.
The consolation on this occasion, however, was that, unlike Inverness Caley the previous week, St Mirren were incapable of finding an equaliser.
Looking to capitalise on Aberdeen’s slip-up against Dundee United the previous day, Rangers had raced into an early lead.
Charlie Adam, back at the ground where he had spent a successful season on loan, swung in a deep cross that looked an easy take for Chris Smith.
Under pressure from Kris Boyd, however, the goalkeeper clattered into defender Kirk Broadfoot, spilling the ball to the unmarked Novo who thrashed it gleefully home from around six yards.
It was a blow for St Mirren as they looked to extend their four-point lead over Dunfermline at the foot of the table but they rallied and only a fine fingertip save from Allan McGregor denied Ian Maxwell an almost immediate equaliser.
The up-tempo start to the match would prove something of a false dawn, however, as the match became bogged down in the midfield with neither side creating anything of note to test either keeper.
Rangers’ next chance in fact came as a result of a St Mirren error, Broadfoot mis-timing a header back to his keeper following Ugo Ehiogu’s long clearance.
Boyd latched on to the chance but could only wastefully lash his shot high into the stand behind the goal.
Moments later and the same player was sidefooting a tame effort into the grateful arms of Smith following good build-up play from Chris Burke and Adam.
St Mirren had the final chances of a dismal first half. Eddie Malone’s deep cross was only parried by McGregor but when the ball fell to Garry Brady on the edge of the box his tame lob attempt drifted well wide. It was a lacklustre effort symptomatic of the half as a whole.
Broadfoot then did well to get in position to connect with David van Zanten’s cross but headed his effort well over the crossbar before referee Charlie Richmond mercifully brought a temporary end to proceedings.
St Mirren looked the livelier side at the start of the second half and, under pressure from Ehiogu, Kean shot over after being picked out by Alan Reid.
Broadfoot then gave the travelling support a glimpse of what they can expect to see from him next season as he jinked past Ferguson and set off up the field, working a 1-2 with Kean before finding the striker again.
The moved ended with a dipping shot from Kean that scraped McGregor’s crossbar.
Rangers’ response was a Boyd header from Adam’s free kick that found the net but from an offside position.
Looking to reinvigorate a deflated-looking Rangers, Smith took off the disappointing Burke and threw on the talismanic figure of Dado Prso for inspiration.
The Croatian was soon involved, striding across the St Mirren penalty box but unable to find sufficient space from which to launch an effort on goal.
Play switched to the other end and ref Richmond was soon dishing out his first yellow card of the game for a quite outrageous dive by Mark Corcoran as he looked to earn his side a penalty.
St Mirren continued to press for an equaliser but Rangers held on to record a precious victory to extend their lead over Aberdeen to eight points.
ST MIRREN: Smith; Potter, Broadfoot, Maxwell (Malone 16); van Zanten, Brittain (Corcoran 61), Murray, Brady, Reid (Mehmet 75); Sutton, Kean
Subs not used: Hinchcliffe, McCay, McGinn, Lawson
Booked: Corcoran (74)
RANGERS: McGregor, Hutton, Weir, Ehiogu, Papac; Burke (Prso 64), Hemdani, Ferguson, Adam; Novo, Boyd (Thomson 90)
Subs not used:Klos, Svensson, Rae, Lennon, Shinnie
Booked: Boyd (80), Novo (85)
Ref: Charlie Richmond