The 18-year-old midfielder was ruled out for the season after suffering a broken bone in his foot, but he is expected to be ready for the next campaign after undergoing surgery in London.
McCoist said on Tuesday: "Barrie travelled down yesterday and had surgery on the broken bone in his foot and we are satisfied that he can now have a good break and be ready for the start of next season."
Lewis Macleod has been absent from the side since January due to knee ligament damage, but McCoist is optimistic that he will return before the end of the season.
"Lewis is going to join us in training this week. He is a good bit off from playing in any part of a game but it is really encouraging," he said.
"I would be delighted if he could get some action before the end of the season for his own confidence.
"I would far rather he had action rather than coming back for pre-season with maybe a little bit of uncertainty about going into a game.
"So, in an ideal world, we can get him some game time and he can go off on his holidays and come back fresh and ready to go."