The former Swansea midfielder scored three times as Roberto Martinez's side picked up its fourth win of the season
The Royals took the lead 35th minute as Sean Morrison rose highest in the penalty area above several Latics’ defenders to head the ball into the top corner.
Roberto Martinez’s men levelled when Gomez tapped in from close range. He doubled his tally for the day when he headed Jean Beausejour’s cross home to give the Latics the lead.
Just as the hosts thought they had the lead secure, keeper Ali Al-Habsi put the ball into his own net as he attempted to push Hal Robson-Kanu’s shot over the bar.
The drama didn’t end there as Gomez scored his hat trick in injury time as he lifted the ball into the top corner to give Wigan all three points.
The Latics were enjoying the majority of possession in the early stages and should have taken the lead in the 12th minute as Beausejour found space down the left and hit a sublime cross into the box for Arouna Kone, who somehow missed a free header from six yards.
The Latics were made to pay for their lack of clinical finishing in front of goal as McDermott’s side took the lead through Morrison, who rose highest in the area to head Shorey’s pinpoint free-kick into the top corner of the net.
The home side finally got the goal it deserved all game when Gomez fired in an equalizer after a great attacking move down the left as Beausejour and Di Santo combined to set up the midfielder. His first effort was saved by Federici but he showed awareness to knock in the rebound.
Reading almost regained the advantage immediately and Wigan was indebted to Al-Habsi, who made a great save to deny Le Fondre as his header looked certain to hit the back of the net.
This time the Latics made the visitors pay for their missed opportunity as Gomez scored his and Wigan’s second of the day as he headed Beausejour’s deep cross past Federici at the back-post into the top corner.
In an end-to-end game the Royals were gifted an equalizer by a bizarre moment from Al-Habsi, as he knocked the ball into his own net as he attempted to clear the Robson-Kanu’s blocked effort over the bar.
However, in the dying seconds Gomez picked up the ball in midfield and drove down the pitch. He fed Kone who returned the pass and the Spaniard fired his shot into the top corner to seal his treble and the win.