Ten men Reading stopped Barnsley's winning run with a 2-1 victory at Oakwell.
First half goals from Gareth McCleary and John Swift did the damage and the visitors managed to cope with losing McCleary after he tangled with Conor Hourihane on 34 minutes.
Adam Armstrong's volley halved the deficit but it proved too little too late.
The Reds had been bidding to win their opening four home games of the season for the first time since 2000.
Paul Heckingbottom named an unchanged side with Josh Scowen and Armstrong making the starting line-up after shaking off knocks.
Reading had an early shot on goal after McCleary burst down the right, his cross found Yann Kermorgant but the Frenchman's effort was deflected over by Angus MacDonald.
The home side responded with Ryan Kent unluckily smashing the crossbar from 25 yards after bursting infield.
The fired up Reds were then caught on the break with McCleary leading the charge before Swift was tripped by Adam Davies for a penalty on nine minutes.
The 'keeper redeemed himself with a save from McCleary's spot-kick but he could only push it back into the midfielder's path for a simple finish.
The home response was good with Adam Hammill forcing a save from Ali Al Habsi.
Cole Kpekawa, on for the injured Aidy White, then crossed for Armstrong whose header was blocked before Hammill skewed an effort over.
Barnsley were then stung on 27 minutes when Swift took advantage of time on the ball to pick his spot from the edge of the box with a thunderbolt.
Barnsley were handed a lifeline on 34 minutes when McCleary was given a straight red card by referee David Coote for pushing over Houihane, who had fouled Daniel Williams.
The sending off livened up the crowd and Hourihane quickly tried his luck from distance but his shot was way over the bar.
Scowen then forced a diving save from Al Habsi by flicking on Hourihane's free kick.
It appeared as though Reading should have gone in at the break with nine men after Williams stamped on Hourihane off the ball but he was let off by the referee.
Barnsley applied pressure right from the start of the second half with Sam Winnall missing a glaring headed chance and Scowen heading over from very close range.
Tom Bradshaw and Saidy Janko, both midweek scorers, were thrown on for the final 20 minutes but it was Armstrong who looked the most likely scorer as he forced another save from Al Habsi before he beat him with a powerful volley on 81 minutes after running on to Bradshaw's header.
Reading managed to cling on to the slender lead through five minutes of added on time with Al Habsi denying Scowen deep into injury time.
Barnsley: Davies, Yiadom, Roberts, MacDonald, White (Kpekawa 17), Kent (Janko 68), Hourihane, Scowen, Hammill, Winnall (Bradshaw 68), Armstrong.Unused: Townsend, Jackson, Morsy, Watkins.
Reading: Al Habsi, Gunter, McShane, Evans, Moore, Blackett, Beerens (Quinn 70), Swift (Obita 52), McCleary, Williams, Kermogant (Mendes 85).Unused: Jaakkola, Harriott, Watson, Kelly.
Referee: David Coote (Nottinghamshire).Attendance: 12, 675 (418).
