But the much-needed win was marred by the 76th-minute dismissal of midfield talisman Barry Bannan, handed a straight red card from Graham Scott for a late challenge on home player Eric Lichaj - Wednesday’s third sending off in their past four away games.
But despite being a man light for the final 14 minutes, the Owls saw the game out in relative comfort and even afforded themselves a late third thanks to Matias’s strike.
Wednesday, full value for their first victory in six matches, made the breakthrough on the half-hour through McGeady’s first club goal since scoring for Everton on the opening day of the 2014-15 campaign.
It represented the Owls’ first goal in 327 minutes, just under five-and-a-half hours.
Carlos Carvahal’s side sealed an impressive away-day success on 62 minutes when Fernando Forestieri seized upon some awful defending from home captain Matt Mills before teeing up Hooper, who coolly netted his 11th goal of the season - and first in six matches.
Gloss was provided five minutes from time when Matias struck his first goal since August 29, with the hosts unceremoniously booed off at the final whistle.
Wednesday merited their interval lead handed to them by McGeady’s milestone strike, with Forest - after a decent enough start - losing their way as the half wore on.
The early sparring saw David Vaughan see his low shot held by Keiren Westwood and Jorge Grant - handed a start with top-scorer Nelson Oliveira missing with a groin problem and loanee Federico Macheda not registered in time to play - off beam following trickery on the wing from Ryan Mendes.
The Owls who made four changes, with Fernando Foresteri, McGeady, Daniel Pudil and Ross Wallace returning to the starting line-up - first announced themselves on proceedings on 11 minutes when Forestieri conjured a chance and saw his stinging low shot from twenty yards out parried by Dorus De Vries, whose alertness saw him hold onto the striker’s follow-up attempt.
Wednesday settled and McGeady skipped past a few challenges before seeing his shot deflected just over before Matt Mills denied Kieran Lee in the nick of time in the box.
The visitors were upping the ante and soon made the breakthrough when Barry Bannan supplied the onrushing McGeady, with space to attack Eric Lichaj down the left and he ran hard at the defender, manoeuvring space before firing home a fierce strike past De Vries.
More pressure also resulted in a second with Bannan’s well-struck half-volley from distance held by De Vries before subdued Forest manufactured their best chance of the half just before the break.
Grant’s point-blank header from Ben Osborn’s left-wing cross was fortunately straight at Westwood, with the Owls having the last word when De Vries, afforded a busy half, denied Forestieri low down.
Forest’s start to the second period was unconvincing with their only semi-threatening moment seeing Grant’s half-volley fly over - with the youngster replaced by Oliver Burke not too long after.
Despite having plenty of the ball, Forest lacked the attacking wit to do anything with it, with the Owls afforded a fair bit of comfort at the back with the frustration among the home supporters starting to grow.
That increased on 62 minutes when the Owls hit a killer second.
They were indebted to some rank-bad defending from Mills, who was dispossessed by Forestieri, who teed up the supporting Hooper, who coolly fired home - the prelude to boos from home supporters.
Westwood was finally called into action to tip over Chris Cohen’s rising shot, but it was all pretty token from the disappointing hosts.
Mendes saw a shot blocked at the far post after Chris O’Grady’s header flashed across the box.
A serene afternoon for the Owls took a turn for the worse 14 minutes from time when Bannan received his marching orders following a late challenge on Lichaj, with Scott showing no hesitation in brandishing the red card.
But it failed to trigger a home response, with the Owls making light of their man disadvantage to add a third late on when a flick on from Athde Nuhiu found fellow sub Matias, whose low precision finish beat De Vries - the cue for him to race to the Wednesday bench to celebrate with players and staff.
Nottingham Forest: De Vries; Lichaj, Mills, Mancienne, Cohen (Walker 82); Mendes, Gardner (Tesche 66), Vaughan, Osborn; Grant (Burke 56), O’Grady. Substitutes unused: Evtimov, Jokic, Wilson, McDonagh.
Sheffield Wednesday: Westwood; Palmer, Lees, Loovens, Pudil; McGeady (Matias 73), Bannan, Lee, Wallace (Lopez 68); Hooper (Nuhiu 79), Forestieri. Substitutes unused: Price, Hunt, Turner, Joao.
Referee: G Scott (Oxon).
Attendance: 20,690 (1,841 Sheffield Wednesday supporters).
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