The former Gers manager failed to lead the club back into the top flight last season.
McCoist took the reins in the midst of the Gers' plummet to the bottom of the Scottish football league and steered the club back in the right direction, gaining successive promotions in his first two seasons.
His bid to make it three in a row was dashed after a series of poor performances and results led to his exit last December.
Rangers failed to clinch promotion in his absence under the guidance of first Kenny McDowall and then Stuart McCall and Ferguson feels McCoist was treated unfairly towards the end of his reign.
"There was a lot of criticism pointed towards Ally McCoist during his time at Rangers," said the former Aberdeen boss.
"You know something, I thought Ally McCoist did a fantastic job under undue pressure and no-one, unless they have been in that position, knows exactly how hard it was."
Adding: "I have no criticism about Ally McCoist. I am pleased that Rangers are looking to step forward from the bad experiences of a few years."
The appointment of Mark Warburton has begun in excellent fashion and has ushered in a new sense of optimism at Ibrox but the achievements of McCoist should not be forgotten.
His presence as a familiar and trusted face, with a real love for the club, was vital during some of the darkest days in Rangers history and his efforts paved the way for the light that now appears at the end of the tunnel for the Ibrox faithful. Many, however, will disagree...