A 68th-minute goal from Yann Kermorgant - his first strike of the season - had looked like securing a smash-and-grab victory for the Royals, only for Pinnock to save the day with his late equaliser, heading home following a right-wing cross from substitute Lloyd Isgrove.
It was the least that the hosts deserved against unambitious opponents, but despite the late respite, the hosts’ alarming sequence extended to a worrying ten matches, with the Reds looking anxious over their shoulders with the relegation zone in clear view.
The Reds are just one point above the bottom three following wins for Bolton and Sunderland, with the Oakwell outfit visiting the latter in a huge game on NewYear’s Day.
The goal from Pinnock was the Reds’ first in almost eight hours as he netted the hosts’ first goal at Oakwell since Zeki Fryers struck in the 2-0 win over Birmingham on November 4.
To say both sides went in the game in desperate need of a morale-boost was by no means an understatement, with the Reds and the Royals having done it tough for spells so far this winter.
Given that, it was perhaps no surprise that a lack of confidence and conviction was apparent in a low-key first half when both goalkeepers were rarely tested.
After a tepid start, the hosts - who went into the game with a poor record of just two home victories in games which had kicked off at the traditional Saturday kick-off time of 3pm in 2017 - did pick up the tempo, but their difficulties in front of goal were self-evident.
A flurry of activity just after the half-hour mark did conjure two good chances, but no goals as their hosts drought without an Oakwell goal continued.
First, Mamadou Thiam - handed a start in a two-pronged forward line with Tom Bradshaw, instinctly fired wide from Andy Yiadom’s cross, while Harvey Barnes should have done better following a pinpoint cross from Adam Hammill, only to glance a header wide under pressure.
Reading had a couple of dangerous moments on the break, with Adam Davies making an early save at his near post to deny Chris Gunter, while a shot from Modou Barrow landed on the roof of the net.
Clearly cajoled to pick up the tempo and urgency, Barnsley were much brighter on the restart and forced Mannone into far more meaningful work.
After Davies held an angled shot from Chris Gunter, play switched to the other end with Mannone grasping a low strike from Thiam before Bradshaw’s shot was blocked.
The hosts were showing the assertion and endeavour, only to be stunned midway through the half when the visitors went in front.
Veteran striker Kermorgant was on hand to clinically head home a quality left-wing cross from Tyler Blackett in a real deflating moment for the Reds.
Paul Heckingbottom soon made a triple substituon from Ike Ugbo, Lloyd Isgrove and Jason McCarthy entering the fray, but it took a while for Barnsley to find their way again.
They upped the tempo at the death with Fryers’ shot tipped over before Pinnock’s late intervention, with a late clearance near his own goalline from Chris Gunter preventing the hosts from nicking a winner as they laid siege in stoppage time.
Barnsley had to work hard for their point but head coach Paul Heckingbottom was pleased his side finally managed to finish off their good build-up play.
He said: “It’s difficult, but I’ll know when I watch it back there’s a lot of good stuff that went off in that game.
“What’s been evident for the last 18 months is a big deficiency in our squad when we’re getting good delivery, being able to score and really be aggressive in the box.
“Between the boxes, it’s fine, with lots of good stuff but there’s a big deficiency at the minute to attack the ball in the box. We pushed big Ethan up at the end and luckily enough it worked for us today.
“It’s pleasing when it’s a young side as well, when you think it’s not going to be your day. We should have had goals but we know why we didn’t.
“We worked (keeper Vito) Mannone, which is pleasing and when you concede, I know it’s a great delivery but it’s something we can do better on defending the ball in the box.”
Barnsley: Davies; Yiadom (McCarthy 69), Pinnock, Lindsay, Fryers; Hammill, Williams, Gardner, Barnes (Isgrove 70); Thiam (Ugbo 70), Bradshaw. Substitutes unused: Townsend, Mallan, Potts, Bird.
Reading: Reading: Mannone; Gunter, McShane, Moore, Blackett; Swift (Aluko 59), Van Den Berg (Evans 62); Barrow, Edwards, McCleary (Böðvarsson 81); Kermorgant. Substitutes unused: Jaakkola, Richards, Evans, Aluko, Ilori, Clement.
Referee: S Hooper (Wiltshire).