The Light Blues were held to a goalless draw at Montrose in a noon kick-off but were confirmed as champions three hours later when a Stuart Leslie penalty secured victory for Elgin over Queen’s Park.
The result at Hampden means nearest rivals Queen’s cannot catch the Ibrox outfit in the title race, as Ally McCoist secured his first piece of silverware as Rangers manager.
His side have looked unconvincing at times this term but have done enough to force themselves over the finishing line with several games to spare, following their demotion to the bottom tier of Scottish football after being consigned to liquidation in the summer and losing their top-flight status.
Rangers made two changes following last week’s drab stalemate against Stirling at Ibrox for the clash at Montrose.
David Templeton and Ian Black returned from injury and suspension respectively to start, with Barrie McKay and Fraser Aird dropping to the bench.
Rangers were handed a tough match the last time they visited Links Park in December, leaving with a hard-fought 4-2 win.
This time around, they started sharply with efforts from Robbie Crawford and Lee McCulloch blocked in quick succession, before Kyle Hutton eventually rifled wide.
Templeton tested the goalkeeper when he collected a Kane Hemmings header before unleashing an impressive half volley that stung the palms of John Gibson.
The winger was threatening again when he cut inside from the left before having another crack at goal but Stephen McNally blocked for a corner.
Templeton then turned provider for Lee Wallace and his effort was touched onto the bar by the keeper, as Rangers kept up the pressure.
At the other end, a Paul Watson strike from distance took a massive deflection and spun just past the upright.
Bolstered by the chance, the home side carved out another couple of decent opportunities.
David Gray - who has netted home and away against Gers this season - forced a save from Neil Alexander, before Alan Campbell glanced a header inches wide.
Montrose should have taken the lead through Martin Boyle but his back post header was off target when he should have had the net bulging.
The home side picked up where they left off in the second half when Gray pounced on a poor clearance from Emilson Cribari and lashed narrowly over the crossbar a minute after the restart.
Rangers had a good chance of their own when Wallace’s cut-back found Hemmings and his shot forced a decent save from Gibson.
Montrose thought they had taken the lead when they had the ball in the net after 65 minutes.
Alexander fumbled an awkward cross that fell for Terry Masson. His shot was saved but the keeper could not hold that ball, which was turned into the empty net by Boyle.
But the goal was disallowed by referee Kevin Clancy for a foul on Alexander.
It looked to be a controversial decision and a let off for Rangers, whose celebrations came later in the day as they made the trip back to Ibrox and took a major step in their road to recovery.