Barnsley suffered their 10th away defeat in 14 Championship games to lose for only the second time in nine games overall.
It is the quickest they have reached double figures for away defeats since 2006-2007 when their 10th defeat came after 13 games.
The Reds failed to score for the eighth time in 28 league games but only the third under Gerhard Struber (from 11 games)
Bristol City's 87th minute winner was the 51st league goal conceded this season, only bottom side Luton have conceded more.
It is the latest the first goal has been scored in a Barnsley game since March 2019 when Jacob Brown made it 1-0 in the last minute at Walsall.
It is the first time Barnsley have been on the receiving end of such a situation in a league match remarkably since March 2014 when Steve Cook scored in the last minute at Oakwell for a 1-0 Bournemouth win.
Since Struber took over 11 goals have been scored in the final 10 minutes of league matches (out of a total of 37)
This was the ninth Barnsley league match to be goal-less at half time this season, and Barnsley have failed to go on to win any of them (D4 L5)
This was the lowest amount of goals in a Barnsley/Bristol City clash in nine meetings, since a 1-0 Barnsley win in September 2012 (the last time the Reds defeated the Robins) The eight meetings in between had produced 37 goals with five 2-2 draws.
Barnsley have now failed to win any of their last 17 trips to Ashton Gate (D5 L12) and have lost each of the last three and five of the last six.
Indeed they have won only one of their last 28 matches in Bristol - defeating Rovers 5-1 in November 1992 (D8 L19)
Ben Williams was drafted into the side at the last minute when Clark Oduor was injured in the warm-up, Barnsley have won only one of the 14 league games in which Williams has played this season (11 starts) compared to three wins in the seven games Oduor has featured (6 starts)
Lee Johnson has now faced former side Barnsley six times in the Championship since leaving the club in February 2016 and is yet to lose (W3 D3), last tasting defeat against the Tykes in February 2015 as Oldham Athletic boss.
Barnsley have had the majority of ball possession in nine of their Championship away games in 2019-2020 (58% this weekend) but have failed to win any of those nine games. Their only away victory this season, at Millwall, saw them share 50%.
The Reds had 16 shots, their joint most on the road this season (also at Blackburn), they lost both those matches.
40. Brad Collins
2. Jordan Williams
3. Ben Williams
4. Kenny Dougall
6. Mads Andersen
7. Jacob Brown
16. Luke Thomas
17. Marcel Ritzmaier
24. Aapo Halme
27. Alex Mowatt (c)
14. Kilian Ludewig (for Ben Williams 71)
28. Elliot Simoes (for Thomas 88)
13. Jack Walton, 19. Patrick Schmidt, 20. Callum Styles, 21. Toby Sibbick, 42. Romal Palmer.
Bristol City Team:
1. Daniel Bentley
2. Jack Hunt
3. Jay Dasilva
6. Nathan Baker
7. Korey Smith
8. Josh Brownhill (c)
9. Famara Diedhiou
14. Andreas Weimann
19. Niclas Eliasson
20. Jamie Paterson
29. Ashley Williams
11. Callum O'Dowda (for Paterson 86)
4. Ádám Nagy, 18. Antoine Semenyo, 23. Taylor Moore, 25. Tommy Rowe, 38. Joseph Wollacott, 42. Han-Noah Massengo.
Bristol City manager Lee Johnson said:
"Barnsley are a really good side. The new manager looks really good. You can see the work he's implemented. They'll be a tough side to play for most teams.
"It was a massive win for us. We needed to apologise, almost, in our performance to the fans. We and everybody else wanted the Liverpool game.
"That's three wins in four in the league and it's starting to look a lot more positive."
Sky Bet Championship results:
FRIDAY 17TH JANUARY 2020
Fulham (3rd) 1-0 Middlesbrough (17th)
SATURDAY 18TH JANUARY 2020
Queens Park Rangers (14th) 1-0 Leeds United (2nd)
Birmingham City (18th) 1-1 Cardiff City (13th)
Bristol City (8th) 1-0 BARNSLEY (22nd)
Derby County (15th) 1-0 Hull City (12th)
Huddersfield Town (20th) 0-0 Brentford (4th)
Millwall (7th) 2-0 Reading (16th)
Preston North End (9th) 2-1 Charlton Athletic (19th)
Sheffield Wednesday (10th) 0-5 Blackburn Rovers (11th)
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Swansea City (6th) 2-1 Wigan Athletic (23rd)
SUNDAY 19TH JANUARY 2020
Nottingham Forest (5th) 3-1 Luton Town (24th)
Grabban pen 90
MONDAY 20TH JANUARY 2020
West Bromwich Albion (1st) 0-1 Stoke City (21st)
Barnsley lie in 22nd place in the Sky Bet Championship with 24 points from 28 games. We are 21 points outside the Play-Offs, 28 points outside the Automatic Promotion Places, 29 points outside First Place and 4 points inside the Relegation Zone.
Up to 21/1/20
Sky Bet Championship Matchday Twenty Nine: Barnsley v Preston North End, Tuesday 21st January 2020. Kick-Off: 7:45pm
On The Road:
FA Cup Fourth Round: Portsmouth v Barnsley, Saturday 25th January 2020. Kick-Off: 3pm