The Rams have not won in four matches in March, and have failed to score in all of them.
"We had the opportunity to score the first goal, which was going to be all-important," McClaren said.
"But we failed to do that. We controlled the game and the performance was great from the players.
"If we hadn't been scoring all season, I'd be more concerned. But we have been.
"We're making chances but sometimes in a season you go through a barren patch. We've just got to keep playing as we're doing.
"Another day, we'd have got all three points. We're attacking well - it's just the end product at present.
"But if we keep going, it will come. We're just missing that icing on the cake."
Derby, who remained third in the Sky Bet Championship standings but fell 10 points behind Burnley, should have gone ahead early on.
The impressive Jamie Ward crossed from the right but Chris Martin's flicked header flew wide.
A well-rehearsed corner move could also have paid dividends for Derby. Ward clipped it to the near post but left-back Craig Forsyth scooped his shot high over the crossbar.
Reading's best chance fell to Royston Drenthe, but he selfishly ignored better-placed team-mates Hope Akpan and Hal Robson-Kanu and drove into the side-netting.
The ebb and flow continued in the second half, with both sides creating chances at will. Derby striker Simon Dawkins could have broken the deadlock but, after a goalmouth scramble, he was too slow to react and the opportunity went begging.
Derby substitute Patrick Bamford played a lively role after coming on in the second half but squandered two openings - the first with a wild shot, the second due to the excellent goalkeeping of Reading's Alex McCarthy.
Adam Le Fondre could also have ended the stalemate but somehow contrived to shoot over from close range after a low, hard cross from Garath McCleary.
In the hectic closing stages, Reading missed two good openings. Akpan was off target with a diving header at the far post and substitute Nick Blackman volleyed too high.
Le Fondre did finally find the net, bundling in a McCleary cross, but was adjudged to have deliberately handled the ball over the line and was booked.
Reading slipped to seventh place, out of the play-off zone, but manager Nigel Adkins was not overly concerned by that.
"I'm not too worried about that," he said. "Our confidence is still high and the players have been top drawer for me.
"There's a lot of positivity about the place. We've been the course and distance before and it's a very exciting time here. We're really looking forward to the last 10 games.
"They're a good side, Derby. We looked to nullify them as they looked to nullify us. I thought we were really strong in the second half. We missed quite a few chances but that's the way it happens sometimes."