Kemar Roofe scored his first hat-trick for the Ibrox club as they repaired the gap at the top to six points after their Old Firm rivals’ 7-0 dismantling of St Johnstone the previous day.
Joe Aribo added a sumptuous fourth for Giovanni van Bronckhorst’s side who now face a potentially season-defining week as they bid to overturn a 1-0 deficit in the second leg of their Europa League quarter-final against Braga at Ibrox on Thursday before next Sunday’s Scottish Cup semi-final against Celtic at Hampden.
Despite the presence of a big Rangers support who filled the stands behind both goals in Paisley, the atmosphere was flat for lengthy periods.
From the perspective of both teams, it was difficult to shake the notion that their Premiership fates had already been determined ahead of the post-split fixtures.
St Mirren had already been consigned to a place in the bottom six by Saturday’s results. Their focus now is on ensuring they are not dragged into the relegation equation but their hopes of taking anything from this contest were rocked inside the opening two minutes.
Roofe’s opener was well constructed by Rangers, Connor Goldson’s long ball picking out James Tavernier on the right before the captain pinged a cross towards Ryan Kent on the opposite side of the penalty area.
St Mirren were slow to react as Kent returned the ball into the six yard box where Roofe had all the time he needed to guide a header beyond Dean Lyness.
Rangers failed to build up any immediate momentum from that rapid start and had to make a change in midfield after just 26 minutes when John Lundstram limped off to be replaced by Steven Davis.
Saints, with ex-Rangers winger Jordan Jones and on-loan Wolves midfielder Connor Ronan prominent, responded brightly without creating any clear-cut openings to equalise.
Rangers suffered another injury blow in first half stoppage time when Filip Helander required lengthy treatment after a clash with Eamonn Brophy and was replaced by 18-year-old Leon King.
In the additional four minutes added, Rangers doubled their lead. Aaron Ramsey should have done so when he struck the crossbar when it looked easier to score but seconds later, Roofe bagged his second headed goal of the afternoon from a textbook Tavernier cross.
With Thursday in mind, van Bronckhorst made two more changes at the start of the second half as James Sands and Scott Wright replaced Ramsey and Kent.
Any lingering prospect of a Saints comeback was ended when Roofe completed his hat-trick in the 50th minute, forcing the ball home from close range at the second attempt after Joe Shaughnessy had initially blocked an effort following good work on the left by Fashion Sakala.
If Roofe claimed the match ball, it was Aribo who scored the best goal of the afternoon. The Nigerian has been struggling to find his top form in the second half of the season but provided a reminder of his quality as he collected a pass from the lively Wright and curled a superb left foot shot high beyond the right hand of Lyness into the roof of the net.