The 31-year-old midfielder had been offered a new contract in the Welsh capital, which he had looked close to signing, but the Scotland international has chosen to move on after three seasons at the club.
Since the end of the Barclays Premier League season, in-demand Cowie has been linked with moves to Rangers, Blackburn and Watford, the club he joined the Bluebirds from back in July 2011. He made 99 appearances for Cardiff, scoring nine goals in the process.
Asked if the Ibrox club had a chance of signing Cowie, McCoist said: "I hope so. Don is certainly a player we have been interested in. I will obviously have to check budgets and things.
"We have been very happy with who we have brought in so far, but if we can continue to add to our squad we will be very pleased.
"It is our job to continue to look out for the best players possible that we can bring to the club and he [Cowie] would certainly come into that category."
McCoist brought new signing Kenny Miller on in the second half of last night's 3-0 win over Highland League club Buckie Thistle at Victoria Park in his side's first pre-season friendly. The Rangers manager was delighted with the contribution that Miller, who slotted home the Glasgow club's third goal with eight minutes remaining, made to the game.
McCoist said: "It was a great finish from Kenny, a really composed finish. But we expect that from him. His link-up play, his overall play and his movement have always been very good.
"It doesn't matter who you are or where you play, when you move to a new club you want to do well and when you are a striker you want to score goals.
"It is a great start for him. I don't have any doubt once we get Kris Boyd back playing in the side he will be exactly the same. No matter what age you are - 14, 24 or 34 - you want to score when you are a striker."
Calum Gallagher, who was one of no fewer than 21 players that McCoist used in the run-out, scored two goals in the opening 45 minutes of the match before being substituted at half-time.
McCoist said "I know it was a pre-season game and I know we made a lot of changes, but at the same time I thought some of our football was more than acceptable. We have to be pleased.
"We didn't want to take a chance with Lewis Macleod or Kris Boyd, but it was important that all of the lads got a run in the side and they did so. I thought they all did well. They will get fitter and stronger and better.
"I was pleased that Calum Gallagher scored a couple of goals. Hopefully, they will be inspired by working with and playing with guys like Kris Boyd and Kenny Miller."
Boyd was left out of the squad against Buckie last night, but McCoist is optimistic he will feature in the next Rangers pre-season friendly, against Brora Rangers at Dudgeon Park on Sunday.
He said: "Kris trained in the morning and did extra running. He had a clean-up operation on his ankle in the summer. There is no problem at all. It is just that he is a couple of days behind everyone else. There is every chance he will get a run-out on Sunday."