Alejandro Faurlin's opener - his first goal for QPR - looked like securing a much needed victory for the London side, who are not yet safe from falling into League One at the end of the season.
But Tom Soares' far-post header in the 77th minute from Tommy Spurr's left-wing cross saved Wednesday from a defeat they could hardly have afforded on the day fellow strugglers Watford and Crystal Palace also picked up away points.
The Owls battled hard at Loftus Road but struggled to create chances.
They also struggled to cope with Rangers' on-loan Tottenham forward Adel Taarabt, whose trickery led to Faurlin's 23rd minute goal.
Taarabt's right-wing cross was flicked on by Damion Stewart and, after a scramble near the edge of the six-yard box, Argentine midfielder Faurlin fired home from close-range.
It was a deserved breakthrough for the R's, who had earlier gone close when Taarabt's corner was headed over by Tamas Priskin and after Faurlin's opener, Priskin almost doubled Rangers' lead four minutes into the second-half.
The Hungarian appeared to be offside when he collected Matt Hill's chip into the area but, as the flag stayed down, Priskin hooked the ball over keeper Lee Grant and onto the bar.
Faurlin and Taarabt brought saves from Grant before James O'Connor missed a chance to equalise, heading Spurr's cross straight at keeper Carl Ikeme.
But Soares made no mistake when picked out by another excellent delivery from Spurr, whose marauding run from left-back was rewarded with a cool finish by the midfielder.
Wednesday survived a late scare when Mikele Leigertwood blazed over but they could have have left the capital with all three points.
Substitute Leon Clarke just failed to connect with another telling Spurr cross as the game ended in stalemate.