First-half goals from Irish trio Noel Hunt, Kevin Doyle and Stephen Hunt set the Royals on their way to a comfortable win, before Doyle completed the scoring with his second in the final minute.
The goal spree takes Reading's tally at home this season to 21 goals in just five home matches, 14 of which have come in the last three games.
Having seen off Sheffield Wednesday 6-0 in their previous home league game, Reading continued where they had left off with three more in the first half here.
Noel Hunt got the ball rolling on 14 minutes with a clinical header from his brother's pinpoint corner, his third goal in as many league starts for the club.
Ivar Ingimarsson should have doubled the lead, but poked over from a Stephen Hunt free-kick, but Reading took complete control of the game when Doyle struck a second on 25 minutes.
Full-back Liam Rosenior made forward progress and pulled the ball back towards Noel Hunt, who appeared to be fouled by Ashley Williams. But there was no need for any penalty decision as the loose ball fell for Doyle to lash home.
"Two-nil to the English" taunted the Reading fans, presumably well aware that both goals against the Welshmen had been scored by Irishmen.
And that soon became a hat-trick of Irish goalscorers as Stephen Hunt got in on the act, stroking home from Jimmy Kebe's low cross.
A double half-time substitution by Roberto Martinez at least injected some spirit into the flagging Swans.
It was more damage limitation than the threat of a comeback, but Jordi Gomez did see a free-kick finger-tipped onto the bar by Marcus Hahnemann before Doyle completed the rout.
Stephen Hunt and Doyle combined down the left and the move ended with a one-two between the pair and a neat Doyle finish with the outside of the boot, his eighth of the season, all of which have come in the last three home games.