The Govan club's record goalscorer and current manager confirmed he has backed with his own money chief executive Charles Green's share issue, which was originally planned to raise £20million.
Green claims to have raised £17million of institutional investment and has ring-fenced £10million worth of shares for fans who have until Tuesday lunchtime to sign up. McCoist is already listed in the share offer prospectus as owning 1million shares in the club, a stake of just under 3%.
The brochure goes on to state that he will have more than 70,000 more shares after the new shares are issued but a smaller stakeholding of less than 2%.
Ahead of Tuesday night's Third Division game against Annan Athletic at Ibrox, the ex-Rangers striker revealed he has given Green's plans for the future of Rangers a "vote of confidence".
"I have personally invested in the club," said McCoist. "I think the best way to put it is that I have bought shares in the club as a fan, I haven't bought them specifically as the manager. I wanted to do it as a supporter and when I am long gone the shares I have invested in the club will be passed down in my family.
"It is obviously close to my heart and like a lot of Rangers supporters will do, I did it on behalf of my family, it's not so much for myself, more for my sons than anything else.
"I have been incredibly boosted by the level of support shown by the fans. In the rebuilding process that we are all part of - and it is the early stages - I wanted to give my own vote of confidence if you like, in buying shares in the club.
"As I say it is something a lot of Rangers fans will do for their own families, hopefully, and being one of them I felt it was something I wanted to do.
"The long-term future of the club is of paramount importance and we are going to do that with the support and help of people around the club. We have plans and agendas for the future and it will be determined by level of support shown from supporters and indeed other people."