Jamie Vardy continued his excellent scoring run with a brace as the Foxes claimed their third successive 3-0 victory.
Leicester have been nigh-on unstoppable since the turn of the year and are now eight points clear of Burnley and 15 clear of third-placed Derby, with Vardy's double taking his record to five goals from his last four matches.
He opened the scoring midway through the first half and then sealed a comprehensive victory for the east midlands side shortly after Danny Drinkwater had doubled Leicester's lead just before the hour mark.
There was little consolation for Barnsley as they were thoroughly outclassed by their opponents, who claimed their first in at Oakwell since November 2010.
Barnsley midfielder Paddy McCourt came in for injured Jim O'Brien in the only change to either side as Tykes boss Danny Wilson and Leicester counterpart Nigel Pearson put their trust in the sides which won at the weekend.
It was no surprise the high-flying visitors, who had beaten Ipswich and Charlton 3-0 in their last two matches, came flying out of the traps early on.
A speculative 30-yard drive from Anthony Knockaert cannoned off the crossbar to give an early warning to the home side, whose goalkeeper Luke Steele did well to get down low and claw away Riyad Mahrez's effort from the edge of the box.
When Barnsley finally did show some attacking intent they were almost caught on the counter as David Nugent's ball over the top put strike partner Vardy clean through but the former Fleetwood man hesitated and a last-gasp tackle from Barnsley captain Martin Cranie snuffed out the danger.
That would be Cranie's last involvement in the match, however, having taken a knock while bailing out his side, and it was his replacement Jean-Yves M'voto who was at fault for Leicester's deserved opener after 21 minutes.
The French defender gave too much space to the in-form Vardy, who comfortably outpaced his marker and drove into the box before comfortably slotting past Steele for his fourth goal in as many games.
That briefly spurred Barnsley into action, but they were nearly caught out again when Nugent, with just the keeper to beat, stumbled at the last moment, while Steele had to be on his guard to grab the ball from Vardy's feet after the ball had taken a deflection into the Leicester striker's path.
Yet on the stroke of half-time, Barnsley almost grabbed an unmerited equaliser when Chris O'Grady put a free header wide and boss Wilson was incensed just after the interval when the striker was not awarded a penalty after going down under pressure from Leicester's defenders.
It was a rare move forward as the Foxes soon threatened the home side's goal, with Mahrez rolling agonisingly wide from a good position before Drinkwater doubled their lead in the 58th minute.
A simple ball upfield found Vardy on the left and his cross allowed Drinkwater to side-foot home on the volley with no one around him.
The provider then scored his second of the night after latching onto Mahrez's ball forward before skipping round the onrushing Steele and tapping into an empty net.
Steele did marginally redeem himself in the closing stages with a point-blank save from substitute Gary Taylor-Fletcher's header but it counted for little as Barnsley remain two points adrift of safety.