The Baggies have, overall, had a hugely disappointing campaign with the team expected to push for promotion at the beginning of the season.
But having started the season under head coach Valerien Ismael, new manager Steve Bruce was only able to steer them to a 10th placed-finish.
The Baggies, though, did give their supporters some reason for optimism on the final day, with a brace from Karlan Grant as well as strikes from Adam Reach and Matt Clarke seeing them to victory at The Hawthorns.
Bruce opted to make two changes from the team that won at Reading when naming his starting line-up.
Having picked up a serious-looking ankle injury midweek, Kyle Bartley came out of the side with Darnell Furlong taking his place.
That change saw Dara O'Shea move to centre-back to partner Semi Ajayi with Furlong at right-back.
At left back, Clarke also returned to the side with Conor Townsend not involved due to the imminent arrival of his first baby.
Elsewhere, Albion lined as expected with Matt Phillips on the right flank, Adam Reach on the left and Jayson Molumby and Jake Livermore cental. Grady Diangana partnered Grant up front.
With their number of absentees stretching into double figures, Barnsley caretaker head coach Martin Devaney named a youthful side with Cauley Woodrow their only outfield player aged over 22.
They began in a 3-5-2 system with Liam Kitching and Will Hondermarck their wing-backs. Woodrow and Aiden Marsh were the front two.
It was the Baggies who dominated the ball in the opening 20 minutes.
And eventually, they started to turn that dominance into chances.
They almost opened the scoring when Grant managed to out-pace Jason Sraha to latch onto a towering header from Ajayi.
Goalkeeper Jack Walton, though, did really well to get down and smoother the striker's shot at his feet.
A minute later and Walton was in action again with the 24-year-old making a smart stop to keep out a powerful Reach drive.
And Albion threatened again in the 26th minute when O'Shea powered a header over following a Phillips corner.
Having been knocking on the door right from kick-off, Albion then went on to net two goals in three minutes.
The first came from the penalty spot and had a huge slice of good fortune about it with Clarke Oduor judged to have fouled Jayson Molumby in the box despite replays showing he clearly got the ball.
Grant, who had missed a last-minute penalty against Coventry in his last outing at The Hawthorns - this time made no mistake and fired in from 12 yards.
In the blink of an eye, the Baggies then doubled their lead with a brilliant finish from Reach.
David Button sent a long ball forward. And with fellow goalkeeper Jack Walton stranding himself in no-mans-land, Reach brilliantly lifted the ball over his head and into the net from 20-yards.
Shortly after the re-start, Bruce's men made it 3-0.
Diangana found Grant in the box who then moved it on to Matt Clarke who was unmarked six yards out.
And in what was probably his last Albion appearance, the Brighton loanee calmly slid the ball past Walton and into the net.
In the 60th minute, it was 4-0 with Ajayi slipping Grant through on goal who brilliantly lifted the ball over the keeper and in.
Albion were then awarded what, this time, was a certain penalty when Liam Kitching fouled Darnell Furlong.
This time, though, Grant failed to score with the forward's low effort well saved by Walton.
The Baggies came a whisker away from grabbing a fifth once again late on when youngster Caleb Taylor, making his Championship debut, produced a powerful header from a corner which Jasper Moon blocked on the line.
Albion (4-4-2): Button, Furlong, Ajayi (Taylor 62), O'Shea, Clarke (Ashworth 67), Phillips, Livermore (Robinson 71), Molumby, Reach, Diangana, Grant.
Subs not used: Palmer, Kipre, Gardner-Hickman, Castro.
Barnsley (3-5-2): Walton, Moon, Sraha, Kitching, Hondermarck (Benson 55), Styles, Wolfe, Helliwell, Oduor (Bremang 61), Woodrow (Adeboyejo 72), Marsh.
Subs not used: Flavell, Christie-Davies, Ariely, Cole.