It's defeat on the road for the Reds in a game turned on its head by red cards.
In a game that Barnsley were in complete control of, a 42nd minute dismissal for Michal Helik changed the entire complexion, resulting in a second consecutive league defeat.
Reds boss, Gerhard Struber made two changes to his starting XI from the midweek cup win at Middlesbrough, bringing Jack Walton back in goal and dropping goalscorer up on Teesside Patrick Schmidt for Conor Chaplin.
The Reds began the game on the front foot, dominant for much of the opening 45, and were unlucky not to go ahead on a couple of occasions.
Inside the first ten minutes, a wonderful cross from the left by Marcel Ritzmaier was met well inside the area by Dominik Frieser whose header looked destined for the far corner only for Royals' goalkeeper Rafael to claw it behind for a corner.
The one-way traffic continued as next it was Luke Thomas teed up by Frieser on the edge of the box who saw a poor effort flash wide, before going on a jinking run that took him beyond two defenders and into the box before seeing his low cross turned behind.
Barnsley's disciplinary issues began on 23 minutes as Mads Andersen took a poor touch on halfway which saw the Reading forward nip in and then fall under the Dane's attempted challenge. Mads was booked for that mistake, but it was still all Barnsley in terms of momentum.
Another fine Ritzmaier cross to the far post from another corner was met by Andersen and his goalbound header struck colleague Michal Helik and went off him and out of play.
There looked a high boot from John Swift for the hosts as he challenged Jack Walton for a high ball. Walton cleared and was floored by the challenge, with just a free-kick awarded by referee Tim Robinson.
The controversy arrived on 42 minutes as after Kilian Ludewig failed to shoot on the edge of the Reading box, the hosts launched a long ball clear which saw Helik scampering back towards his own goal alongside Royals' striker Lucas Joao and as 'keeper Walton cleared the ball, both Helik and Joao came together and referee Robinson adjudged it to have been a deliberate foul by the Pole, sending him off and thus reducing the Reds to ten men.
Reading finally had one or two forays into the Reds' third following that, but Barnsley hung on for half-time, with players surrounding the officials going in 0-0 at the interval.
HALF-TIME: Reading 0-0 Barnsley
Struber brought Callum Styles on for Luke Thomas at the break, with the Reds trying to sit in a little being a man light.
Josh Laurent was booked for a crude tackle early into the second 45 before Frieser was flattened on the edge of the box by Royals' 'skipper Liam Moore, with the referee not even giving the Reds a free-kick.
A few minutes later and Olise for the home side went straight through the back of Chaplin on halfway with a free-kick given and nothing more.
Schmidt replaced Frieser soon after before Reading substitute Yakou Meite forced Walton into his first save of the game, wonderful to his left to push behind the powerful header.
But straight from that set-piece, the same player bundled in the opening goal after the Reds failed to clear the inswinging corner kick.
If it wasn't a hard enough task already, it became tougher a moment later, as Andersen joined Helik in the dressing room, sent off for handball on 68 minutes.
There was a booking for the captain, Alex Mowatt before Reading sealed the victory when again, Barnsley didn't clear a corner with any real purpose and Olise struck a first time effort into the bottom corner from 25-yards with Walton unsighted with bodies in front of him.
The hosts settled with what they'd got from then on in, as the Reds tried to rally with nine men, but it was to no avail as Struber's men fell to a second successive league defeat on an awful afternoon in Berkshire.
FULL-TIME: Reading 2-0 Barnsley
Walton, Ludewig, Sollbauer, Helik, Andersen, J.Williams, Mowatt, Ritzmaier, Thomas (Styles), Chaplin (Halme), Frieser (Schmidt).
Unused: Collins, Miller, Adeboyejo, Woodrow.