Right-back Foley, whose cross had been turned into his own net by Bobby Hassell to gives Wolves an 18th-minute lead, struck the clincher four minutes from time when he drove home a low shot from Sam Vokes' cross to earn Wolves a second successive home win.
Wolves looked anything but Championship pace-setters for long spells of the game and Barnsley had enough of the match to have taken some reward but were unable to turn their smart attacking play into goals.
The lively Jamal Campbell-Ryce was a constant thorn in the side of the Wolves defence who also had their work cut out keeping Jamie Cureton in check.
However, Wolves had just enough steel and determination about them to hold on to their advantage before Foley eased their nerves once and for all.
Foley had given a sign of how dangerous he could be when he forced Heinz Muller into an acrobatic tenth-minute save.
But before Wolves made full use of his attacking intent, Barnsley enjoyed a purple patch. Diego Leon twice threatened from long range in between goalkeeper Wayne Hennessey just about getting away with spilling a Jon Macken cross at his near post.
It was only a brief flurry from Barnsley but the manner in which they fell behind was unfortunate to say the least.
Michael Kightly and Sylvan-Ebanks Blake combined to release Foley who delivered a curling cross into the area that Hassell turned into his own net from six yards while under pressure from Andy Keogh.
Barnsley did try and mount an immediate response but Richard Stearman was well-placed to block a shot from Steve Foster while Hennessey got down low to deal with a drive from Campbell-Ryce before Macken shot just over the bar.
Having survived that spell of pressure, it was ironic that Wolves almost doubled their lead on the stroke of half-time.
After being set-up by David Edwards, Keogh pounced from 12 yards only to see Marciano van Homoet clear his shot off the line.
Barnsley continued to dictate the play in the second period, but Wolves always looked more threatening because of the firepower they possess.
Stearman just failed to convert Kightly's free-kick before Barnsley's best chance of an equaliser was headed over the bar by Cureton after another centre from Campbell-Ryce.
Vokes should then have eased Wolves' nerves once and for all when he only had Muller to beat but the young Welshman was denied by the German keeper.
But Muller couldn't stop Foley's decisive 86th-minute shot that slid under his body.