McCoist's side booked their place alongside the SPFL Premiership leaders in the second round of the League Cup with a narrow 2-1 victory at the Excelsior Stadium last night.
Goals from Kris Boyd in either half of the game ensured the Ibrox club secured a match against the top-flight leaders at home - probably on Tuesday, September 16.
But the Gers boss was furious his charges allowed their bottom-tier rivals to equalise and admitted they will have to play better against John Hughes' side. "I was pulling my hair out in the first half at the free-kicks we were giving away," McCoist said.
"We were giving Queen's Park an opportunity to put the ball into the box.
"I didn't think they would pose us as many problems as they did from open play. But our lack of discipline, the fact that we gave away silly free-kicks and gave them an opportunity, was a concern.
"And it turned out that my concern was justified. We didn't defend a free-kick at all and that let Queen's Park back into the game.
"That said, I thought we started the game very well and did well in the first 10 to 15 minutes.
"We scored a great goal, had one disallowed and looked really dangerous.
"We were very, very disappointed to come in level at 1-1 at half-time. The next goal was always going to be very important and thankfully we got it.
"We could have had another one. We hit the post and had a couple of chances we could have done better with. There are certainly positives to be taken from the game and the biggest one is we have a home tie with Inverness to look forward to.
"They haven't lost a goal in the league. They are playing really, really well just now. We will need to have a lot more discipline in that particular game.
"I was disappointed we gave away the set play for their goal. I am not sure that Simmo had to come for it. But once he comes he has to take it. With hindsight he should have left it for Bilel to take. It was a sore one for him and for us to take."
Boyd, who scored a hat-trick in the Petrofac Cup win over Clyde last week, took his tally for the 2014/15 campaign to five with his double.
The Gers manager was delighted with the prolific striker's contribution.
"I thought Kris's first goal was excellent and the way he held his position for the second goal was good," he said. "A lot of forwards would have got sucked in.
"But that is what he does. If we can supply him with chances in and around the penalty box and six-yard box he will score."