A wonder-goal and slice of good fortune gave Millwall the points in the opening clash of the Professional Development League on Oakwell's Academy pitch.
Chances were aplenty for the Reds but they just couldn't hit the back of the net, as Maris, Oates, Boakye-Yiadom and McKnight all went close for Paul Heckingbottom's side.
The Lions opened the scoring in spectacular fashion from absolutely nothing on 25 minutes, as Dylan Casey volleyed home from 30 yards past the admiring Dibble.
Neil Harris' side doubled their lead just two minutes into the second half as Dibble's clearance smashed into the face of Pavey, and the striker could barely see as he bundled home before falling to the deck in need of treatment.
Barnsley went on attack after attack with Oates showing good pace on 63 minutes before thumping just over the bar from just outside the area.
Just two minutes later, Darren McKnight cut the Millwall defence in two with a brilliant ball down the middle that Maris latched onto but could only scuff wide with his left peg.
Three minutes past the hour saw Dom McHale scoop over after tricking his way into the box from the right-hand channel and then Boakye-Yiadom's header skimmed the top of the bar from McKnight's corner.
Reds: Dibble, Bree (Gooda 46), Noble-Lazarus, Cowgill, M'voto (Holgate 46), McKnight, Digby, McHale (Kassouri), Maris, Oates, Boakye-Yiadom.
Millwall: King, Siafa, Casey, Thompson, Goodman, Wood, Webb, Powell, Pavey, Philpot, Farrell.