Shiels has been at the forefront of recent speculation on his future at the third-tier club as Rangers prepare to make cutbacks in their budget, which currently sees the club part with around £1m per-month.
McCoist did not confirm whether Shiels will be leaving Ibrox this month, but he was happy the player proved his worth on only his third start of the season.
"We're absolutely delighted with the reaction of Dean. He was obviously a bit concerned about not starting as many games as he'd hope," said McCoist.
"That, obviously, is a good thing for me, because you want that from players who aren't involved.
"He was very receptive to the fact that the team had been winning and it's difficult to dislodge players when you're on a successful run.
"He quietly waited for his chance and with the injuries we saw today, he came in and he played particularly well."
East Fife boss Gary Naysmith praised his team's spirit as they continued to battle despite losi9ng the opening goal after only three minutes.
Naysmith said: "We got off to a really disappointing start. The first three passes from the back straight to Rangers players gave them the initiative.
"We gradually grew into the game. But definitely in the second-half at 1-0, we had some good chances. It would have been interesting game if we had gone level.
"I couldn't ask any more from the players. It was important we showed we were improving as a team."