The 23-year-old has been a player McCoist has pursued for some time and the boss was delighted to secure his signature on deadline day.
And the Rangers boss says it marks a continuation of the project of restoring Rangers to the top of the game.
Templeton signed a four year and McCoist believes he is just one of a number of players who will have an instant impact while also continuing to develop as a player.
McCoist said: “I think it’s important for everyone to remember exactly where we are in the rebuilding process and also to let people know that we are planning for the future.
“You look at some of the lads we have in our team at the moment, like McKay, Macleod and Crawford and some of the guys we have brought in like Sebastien Faure, they are a good age.
“They have the best years and the majority of their footballing careers ahead of them and that’s important because we have to start gelling together and blending and building for the future.
“Our main objective this year is to win the league, and we won’t take that for granted, but if we can do that and bring some younger players in to the team at the same time then that would be a real bonus.
“David has always been a player that has caught the eye of most football supporters even out with Hearts.
“All football fans are excited by players of that type who entertain with the ball and we’ve been admirers of his for a long time.”
Templeton was famously named after one of Rangers’ greatest ever players when he was handed the middle name Cooper and McCoist admits if he can go anywhere close to emulating the legendary Rangers star he will be one of his best ever signings.
“If he’s got half the talent of the Cooper that I played with I’m sure the fans would settle for it and so would I.
“It’s certainly something to have the same name as one of the greatest wingers, indeed players that our club has ever had.”