Long has endured a frustrating season of cameo roles so far this term, culminating in an on-pitch argument with Stephen Hunt in Tuesday's win over Blackpool, when Hunt refused to allow his Republic of Ireland team-mate to take a penalty.
This time, Long's patience was a virtue as he came off the bench with just ten minutes left to help Reading see off Norwich's stubborn resistance.
Long won Reading a penalty six minutes from time when his pressure caused Mark Fotheringham to handle and the substitute watched on as Hunt again took responsibility from the spot.
That attitude earned Long his reward two minutes later when he raced to the near post to head home his second goal of the season after great work down the left by fellow sub James Henry.
It was ultimately a deserved win for the promotion-chasing Royals, but they had to grind the visitors down as both sides tried to play football on a heavy pitch.
And Steve Coppell's ability to spark life into his side with some lively additions from the bench eventually proved the difference between the sides.
Reading brought in Aussie keeper Adam Federici for his first league start of the season, Marcus Hahnemann's calf injury ending a run of 100 consecutive league starts for the regular number one.
Kalifa Cisse also returned at the expense of Brynjar Gunnarsson, while captain James Harper replaced teenage wingman Henry.
Norwich were forced into one change, as on-loan Reading striker Leroy Lita was unable to play against his parent club, captain Fotheringham coming in to force a positional reshuffle.
Lita would have relished the early chances which fell Norwich's way - Darel Russell scuffing in front of goal from Jon Otsemobor's low cross on six minutes before Matty Pattison headed Lee Croft's cross wide as Federici hesitated.
But Reading gradually took control as first James Harper and then central defender Ivar Ingimarsson saw side-footed efforts fly just wide of the post.
Noel Hunt flashed a header over the bar on 64 minutes as Reading started to raise the pressure but when the goal came it arrived courtesy of a big helping hand - literally - from Fotheringham.
He handled under pressure from Long, allowing Stephen Hunt to step up and fire home from the spot, although Marshall got his hands to the penalty only to see the effort bounce in off a post.
Two minutes later, Long got his goal, heading home Henry's cross to keep Reading in sight of the promotion places.