The two summer signings produced scrappy second-half finishes to add to Ben Watson's screamer before Shaun Maloney completed the scoring for the FA Cup holders at Oakwell.
Barnsley struggled throughout and were forced to play the final 25 minutes a man down after substitute Dale Jennings was dismissed moments into his Tykes debut for a challenge on James McCarthy.
Wigan playmaker Maloney had the first clear-cut chance of the game in the 13th minute but his first-time left-foot effort at the back post was blocked by the legs of Barnsley goalkeeper Luke Steele following Jean Beausejour's left-wing centre.
The Tykes responded five minutes later when midfielder Jacob Mellis'goalbound strike was blocked by the Wigan backline before the resultant loose ball was scrambled behind for a corner with striker Chris Dagnall ready to pounce inside the six-yard box.
Wigan players felt they should have had a penalty just before the midway point of the first half but referee Geoff Eltringham dismissed the appeals following a coming-together between Latics defender Barnett and Barnsley's Scott Golbourne.
The visitors were not to be denied an opener for long and made the most of their superiority in possession eight minutes before the break when central midfielder Watson picked up the ball 25-yards from goal and drove a powerful effort into the bottom left corner beyond the dive of keeper Steele.
Latics midfielder McCarthy went close to doubling the away side's advantage when his 42nd-minute shot from the right-hand side was repelled by Barnsley captain Steele.
Wigan missed two presentable opportunities to extend their lead in the opening minutes of the second half before debutant Holt eventually gave Owen Coyle's side breathing space in the 54th minute.
Frontman Holt, a £2million summer signing from Norwich, diverted home a goalbound strike from Latics captain Emmerson Boyce after the hosts failed to fully clear a right-wing corner.
Barnsley's day then went from bad to worse when Jennings was shown a straight red card on the hour mark, five minutes into his Tykes debut. The former Bayern Munich man lunged at Wigan midfielder McCarthy just moments after replacing left-back Tom Kennedy and referee Eltringham had little hesitation in dismissing the 20-year-old.
The hosts failed to create a clear cut chance throughout the game and Wigan made the most of their numerical advantage in the final stages to add to the scoreline.
Central defender Barnett poked in past Steele from close-range to put the contest beyond doubt 11 minutes from time before Maloney completed the rout with a simple tap-in in the 88th minute following a pull-back from substitute Marc-Antoine Fortune.