Kevin Doyle's second-half double took him past a half century of goals for the Royals, who put four past the Rams on the final day of last season as the pair waved farewell to the Premier League.
On this evidence, only one of these sides will be making an instant return as Reading dominated from the moment Noel Hunt made the breakthrough after 20 minutes.
He flicked home a header from a tight angle following a corner from his brother Stephen's corner.
It was a deserved lead for Reading who had already seen a goal disallowed as Noel Hunt was penalised for tugging Emanuel Villa as the Argentine headed a free-kick into his own net.
Noel Hunt then had a second effort disallowed when he swept home from close range after Doyle had headed back another Stephen Hunt corner, only for a linesman to indicate Doyle's assist had been from behind the bye-line.
In between chances, Jimmy Kebe saw a stinging volley flash wide from Chris Armstrong's superb cross-field pass and Derby would have been pleased to go in at half time only one down.
They had a chance to level early in the second half when Kris Commons was given time to shoot, only to blaze high and wide.
Reading secured the two-goal cushion they needed midway through the second half when left-back Armstrong held off the challenge of Nacer Barazite and sent in a perfect cross for Doyle to head home from close range.
It was the striker's 50th goal for Reading and his 12th in the league this season - and a 13th was not far behind.
Reading thought they had been awarded a penalty when Claude Davis clashed in mid-air with Ivar Ingimarsson, only for referee Scott Mathieson to inexplicably award the foul against Ingimarsson.
But Reading inflicted swift retribution of their own as the ball quickly found its way out to Doyle, who turned and struck from 20 yards with a shot which fizzed past a stunned Stephen Bywater.
Miles Addison should have pulled one back for Derby but saw his downward header from point-blank range bounce over and sub Barazite produced a save from the previously redundant Marcus Hahnemann.
But Stephen Hunt nearly put the icing on the cake for Reading five minutes from time with a dazzling run that set up a one-on-one with Bywater, only for Davis to produce a superb last-ditch tackle to deny the midfielder.