The Iron were undone by first-half goals from Keith Treacy, Billy Jones and Iain Hume.Scunthorpe's first-half display was as bad as anything witnessed in the Championship all season and on this evidence they will playing their football in League One next term.
Baraclough's men failed to create a single opening in the opening 45 minutes, much to the disgust of the home supporters who booed their team off at half-time and again at the final whistle.
Treacy crossed from the left flank after 19 minutes and Eddie Johnson headed over the crossbar and then Chris Brown shot over from inside the 18-yard box.
Brown was wasteful again in the 31st minute when he nodded over from Ricardo Gardner's superb delivery but the breakthrough arrived a minute later.
Hume broke from deep and slipped a superb pass into Treacy, who beat the offside trap and drilled a low right-foot shot into the bottom left-hand corner.
The Iron had played for several minutes with only 10 men on the pitch as Andy Hughes was receiving treatment for a facial injury.
Andy Wright was quickly brought on after the goal, but the visitors had their noses ahead.
Five minutes later Preston had their second when Treacy's inswinging corner from the right was missed by every Iron player and found Jones who bundled home from point-blank range.
Johnson blazed wide from eight yards out in the 40th minute from Hume's intelligent pass and Preston claimed their third two minutes before the break.
A deep cross into the box was headed down by Brown into Hume's path and the Canadian stooped to nod into the net from six yards.
Baraclough made a substitution shortly before the hour mark and another just after but it was Preston who looked more likely to add any further goals.
Johnson was wasteful again when he tried to dribble his way through the home defence and when Scunthorpe striker Joe Garner hit a 20-yard shot into Iain Turner's arms with 15 minutes remaining, it was the hosts' only effort of note during the entire 90 minutes.
The second-half was most noticeably for Iron fans clearly turning against Baraclough, with chants from the terrace including "You're getting sacked in the morning" and "We're shit and we know we are".