Reading chalked up a fifth consecutive League win to maintain their stranglehold on a play-off place and choke Rotherham's own top-six dreams.
First-half strikes from James Harper, Andy Hughes and Nicky Forster underlined a dominant display by the Royals, who were in control from the first whistle.
They should have been ahead inside three minutes, unmarked midfielder Hughes shooting wide after a mazy run down the right by on-loan Manchester United winger Luke Chadwick.
But the bright start bore fruit on 15 minutes as Reading went ahead. Again it was the trickery of Chadwick that opened Rotherham up and his run and pass allowed Forster to tee up Harper for his first goal of the season courtesy of a clinical finish.
Rotherham were almost level in bizarre circumstances midway through the half when Adie Williams deflected a pass beyond his own goalkeeper, forcing Graeme Murty to scramble off the goal-line.
But the home side continued to dominate with Chadwick and the lively Hughes causing all sorts of problems.
Hughes had penalty claims waved away when he spun past Marvin Bryan and then tumbled under the defender's recovery challenge, but Hughes' luck changed on 33 minutes.
His precision pass sent Forster clear through the middle and when the striker played a return pass Hughes was on hand to rifle an unstoppable shot into the top left-hand corner.
And the game was up for Rotherham five minutes before half time when Hughes returned the compliment to Forster with a perfect cross for the striker to slide in at the far post.
After Reading's electric first-half display, the second period was always likely to be an anti-climax.
Bryan escaped a second penalty claim when he appeared to block Forster's cross with a hand as Reading continued to dominate and Rotherham's hopes of a consolation were dashed when substitute Andy Monkhouse's effort was ruled out for offside.