Reading goals in either haf from Meite and Puscas were enough to end the Reds' winning run here at the Madejski Stadium.
Gerhard Struber had made two changes to the XI that had won in midweek at Hull City with Marcel Ritzmaier and Kilian Ludewig replacing Luke Thomas and Mike Bähre.
It was to be a very disappointing first half showing from the Reds who struggled to retain possession and were very wasteful in front of goal.
The hosts looked sharper, partucularly in midfield with the on-loan Ovie Ejaria a constant menace and he tested Brad Collins' reactions with a stinging shot from 20 yards out in the eighth minute.
Barnsley attacks were rare but looked promising if only their final ball wasn't letting them down in key moments. Both Alex Mowatt and Cauley Woodrow were guilty of poorly timed through balls.
Reading took the lead when John Swift's free-kick was headed towards goal by Michael Morrison, touched on by Yakou Meite and despite the efforts of Jacob Brown and his 'keeper, the ball trickled agonisingly over the line.
Brown would take aim from the edge of the box soon after in an attempt to make amends but his effort whistled a few inches wide - it was a close call indeed.
Conor Chaplin then blazed an effort over after a far post cross by Mowatt found the little man inside the box and soon afterwards there were bookings for Mowatt and Jordan Williams for pulling back Ejaria in separate incidents who was breaking on halfway.
With 42 minutes played, Woodrow capitalised on a defensive mistake and headed towards the box with a couple of minutes left in the half, but once inside the area he dragged his effort well wide of the post. It was a huge chance missed, especially with Chaplin, Brown and Mowatt all waiting for a pass.
And to compound the Reds' misery, Woodrow was thwarted twice more in stoppage time as after a great tackle from Ludewig he broke down the right, fed Cauley on the edge of the Royals box and the top scorer saw his effort saved to the 'keeper's right but Woodrow got a second bite at the cherry and sent a follow-up arrowing towards the top corner only for Rafael in the home net to wonderfully tip the ball over.
HALF TIME: Reading 1-0 Barnsley
There was a half-time substitution for the Reds as Thomas came on for Oduor as Struber looked for a reaction.
But whilst the football improved somewhat after the break, there were less opportunities created and it was Reading who doubled their lead on the hour-mark as George Puscas spun Aapo Halme just over halfway, advanced goalwards and then bent home a beautiful finish into the bottom corner from 20 yards out for 2-0.
Barnsley's task had become even tougher now, with the Biscuitmen soaking up the pressure, sitting deep and looking to hit the Reds on the break.
Patrick Schmidt and Mike Bähre were introduced, replacing Ritzmaier and Chaplin, but the hosts remained able to hold off Barnsley for the most part. Plenty of possession for Struber's side, but their shooting and final balls were way off the standard required on a frustrating afternoon in Berkshire.
Thomas looked lively and linked up well with Ludewig down the right on a number of occasions but it proved to be one of those days for Barnsley. Nothing was coming off.
There were late efforts from both Woodrow and Bähre as we approached the final 10 minutes but both shots were wide of goal, with Reading now sat in and happy to protect their lead.
A hugely disappointing afternoon for the Reds, and the gap to safety grows to five points with ten games remaining in the Sky Bet Championship season.
FULL TIME: Reading 2-0 Barnsley
Collins, J.Williams, Sollbauer, Halme, Ludewig, Oduor (Thomas), Mowatt, Ritzmaier (Bähre), Woodrow, Chaplin (Schmidt), Brown.
Unused: Walton, B.Williams, Dougall, Simoes.