Doyle, whose Roy of the Rovers career has taken him from Cork City to the top flight, hit the target after just 16 seconds, with a stunning strike with South Korea international Seol Ki-Hyeon snatching the second before Rob Hulse hit back after the interval.
Reading , who picked up four points off United last season, snatched the lead in dramatic fashion after United lost possession after kicking off.
Doyle outpaced Chris Morgan and surged towards the box, reserve keeper Ian Bennett, in for injured Irish Republic international Paddy Kenny raced off his line but was helpless as Doyle slammed his left-foot shot into the net from 16 yards.
Midfielder Chris Armstrong tested Reading keeper Marcus Hahnemann with a long-range strike and Paul Ifill clumsily volleyed a David Unsworth corner before Reading almost snatched a second, Seol Ki-Hyeone, a £1.5million signing from Wolves firing in an angled drive, tipped round the post by Bennett.
United were in trouble again in the 17th minute as midfielder James Harper, cut in from the left, with Phil Jagielka in hot pursuit finishing with a low shot from the edge of the box but with Bennett beaten, the ball crashed against the foot of the far post.
Leroy Lita had a close range effort blocked before Reading added a second on 25 minutes, Lita picking out Seol, who turned Chris Morgan to power a left-foot strike into the bottom left hand corner from 18 yards.
United boss Neil Warnock brought on Keith Gillespie and Alan Quinn for David Unsworth and Ifill at the start of the second half.
The Sheffield side, booed off at the interval, battled back and made it 2-1 on 61 minutes, Ade Akinbiyi stretched to head the ball to Hulse who turned Ibrahima Sonko to score from the tightest of angles.
Graeme Murty got in a tangle with Soko and almost let in Akinbiyi with Reading forced back. Gillespie almost snatched a point late in the game with a stunning strike from the edge of the box as Hahnemann stretched to tip the ball round the woodwork.