United legend Steve Coppell nearly masterminded a glorious win over his former club as his Reading side led through a second-half Kevin Doyle penalty after Gary Neville had handled.
But the former Old Trafford winger was denied by a current United wide boy as Cristiano Ronaldo rescued the visitors with a superb strike 17 minutes from time.
Ronaldo brilliantly controlled a John O'Shea pass and cut inside Graeme Murty before unleashing a fierce low drive beyond the reach of Marcus Hahnemann in the Reading goal.
But Reading held on to secure a point, extending an unbeaten home run that stretches to the first day of last season.
The result had looked unlikely early on as United started at a fierce pace. Wayne Rooney's second minute shot was spilled by Hahnemann although the keeper redeemed himself by blocking the follow-up from Kieran Richardson.
But Reading composed themselves, with striker Leroy Lita looking lively as he gave United centre-back Gabriel Heinze a real headache.
The striker nearly set up Ki-Hyeon Seol with a neat low centre, although the South Korean winger could not get ahead of Heinze in time to turn the ball home.
And Reading were presented with a golden opportunity to break the deadlock on 18 minutes when Bobby Convey's flicked centre deflected into the path of Doyle, who took too long to set himself and saw his close-range effort well blocked by Edwin Van der Sar.
The United keeper then got down well to hold a stinging low drive from Seol as Reading began to grow in confidence.
But United served several reminders of their threat, Hahnemann spilling a fierce curling free-kick from Ronaldo, and was grateful to see his defenders hack the loose ball clear.
Hahnemann redeemed himself with a tremendous fingertip flick to take the ball off Paul Scholes' toes as the midfielder seemed certain to turn in Ronaldo's low cross.
But it was Reading that made the breakthrough three minutes into the second half, with the opportunity literally handed to them by England full-back Neville.
Opposite number Murty sent over a teasing cross from the right and the ball evaded everyone before bouncing off Neville's arm, referee Peter Walton instantly pointing to the spot.
Doyle, who had missed Reading's Carling Cup shootout win over Darlington in midweek, stepped up to slam home the spot-kick, although Van der Sar got a hand to the effort before it crept into the corner.
Predictably, United hit back menacingly, Rooney pulling the ball back invitingly, only for the hapless Richardson to manage a complete air kick.
Centre-back Ivar Ingimarsson brilliantly blocked a Scholes shot when the midfielder looked destined to score, but United finally got back on level terms on 73 minutes.
Ronaldo pulled a high ball down brilliantly and had space to run at Murty before firing into the far corner with Hahnemann unable to react quickly enough.
Substitute John O'Shea might have stolen all three points for United late on, but his free header from a Michael Carrick corner was flicked away by the impressive Murty.