Callum Reilly’s stunning 35-yard strike got Blues under way before a second-half double from Akwasi Asante helped the visitors see off two fightbacks from the Tykes.
Blues largely outclassed their hosts in the first-half but were left disappointed to find themselves level at the break as Danny Rose’s goal on the stroke of the interval cancelled out Reilly’s 23rd minute opener.
Asante fired Blues ahead in the 58th minute before Matty Steade pegged back for Barnsley in the 70th minute. However striker Asante made it four goals in his last two games by bagging the decisive strike five minutes later.
Barnsley rarely tested their opponents in the opening half and it looked inevitable that Richard Beale’s side would open the scoring.
Ryan Higgins, Jack Deaman and trialist Ibrahim Farah all tested Lukas Lidakevicius in the Barnsley goal in the opening stages and it wasn’t until the 20th minute when Blues ‘keeper Nick Townsend was called into action to keep out a tame Erico Sousa effort.
Midfielder Reilly opened the scoring in style as he picked the ball up all of 35 yards out before sending an accurate effort beyond the outstretched Lidakevicius.
Blues pushed for a second; Farah trying unsuccessfully from distance on two occasions.
However Barnsley caught the away side on the break from a corner seconds
before half-time to level. Striker Rose nipping in to fire past Townsend.
Having bagged two during the 4-1 win at home to Huddersfield on Bank Holiday Monday, Asante continued his goal-scoring form in the 58th minute.
Mitch Hancox, playing in central midfield, thread a pass through for Asante to latch on to and he coolly finished from just inside the area.
Yet Barnsley weren’t prepared to lie down and levelled again with 20 minutes remaining. Josh Alderson’s cross from the right beat Townsend and found the head of Steade inside the six-yard box.
But Blues weren’t prepared to let the three points slip with a place at the top of the table in their sights.
The winner arrived 15 minutes from the end. Substitute Brice Ntambwe’s pass found Asante down the left, the burly frontman cut inside and took his time before directing a low shot inside the left post.
Barnsley thought they’d grabbed a late equaliser but both captain Will Packwood and Deaman were on guard at the back to deny Rose and then substitute Rhys Oates.
Barnsley U21s: Lukas Lidakevicius; Josh Alderson, Jake Scott (C), Brad Kilburn, Matty Steade; Erico Sousa (Rhys Oates 63), Jordan Clark Sam Patterson, Andre Ntambwe (Brad Abbott 63); Reuben Noble-Lazarus, Danny Rose.
Subs not used: Macaules Skiletto, Omari Alexander-Skelton, Elliot Chanderton.
Goals: Danny Rose (44), Matty Steade (70)
Blues U21s: Nicholas Townsend; Ryan Higgins, Jack Deaman, Will Packwood (C), Ben Gordon; Callum Reilly, Matthew Rickard (Brice Ntambwe 63), Mitch Hancox; Ibrahim Farah (Reece Hales 78), Akwasi Asante, Josh Hawker (Reece Brown 71).
Subs not used: Callum Preston, Nathaniel Kelly.
Goals: Callum Reilly (23), Akwasi Asante (58 and 75).