Player of the year Conor Hourihane scored one and set up three as Barnsley ensured an unhappy return for former boss Keith Hill to Oakwell.
Josh Scowen scored two headers and Mason Holgate another, all from Hourihane corners to put the Reds in command against ten man Rochdale.
And after Hourihane hit one of his own, Sam Winnall netted to round off the afternoon and the season in style for Barnsley.
Ben Pearson volleyed wide for the Reds after being played into a good position by youngster George Maris in Barnsley’s best first half chance against Rochdale.
Adam Davies had to be alert to race off his line and close down Henderson when the Dale striker was played in.
James Bree fired over for the Reds from just outside the area.
And Smith tested the reflexes of Dale keeper Josh Lillis with a long range effort.
Barnsley’s chances of seeing out the season with a win increased after Joseph Rafferty was sent off.
Rafferty received his marching orders for a second yellow card with 48 minutes gone.
But it was the visitors who went closest to scoring when Reuben Noble-Lazarus saw a shot blocked before Ian Henderson fired the rebound wide.
Scowen headed a nine-minute double for Barnsley as they raced clear.
Scowen rose to meet Hourihane’s cross to put the Reds in front after 67 minutes.
And the two combined once again for Scowen to head home once more with 14 minutes to go.
Holgate ensured there would be no doubts over the result when he headed home the fourth on 84 minutes.
Rhys Oates slotted in Hourihane to tap home his goal on a superb afternoon for the Irish midfielder.
And Winnall turned in a George Smith cross to wrap up the afternoon.
Barnsley: Davies, Bree (Oates 70), Holgate, Nyatanga, Smith, Pearson, Hourihane, Berry (Digby 77), Scowen, Winnall, Maris (Williams 66).
Subs not used: Dibble, Lalkovic, Cranie, Abbott.
Rochdale: Lillis, Rafferty, Eastham, Lancashire, Vincenti, Noble-Lazarus (Camps 69), Tanser, Logan (Allen 50), Cannon (Bennett 46), Kennedy, Henderson.
Subs not used: Diba, Andrew, Bunney, Rose.