The Gers continued their stunning start to the season with a 6-1 rout of Forfar at Ibrox, with Nicky Clark bagging four goals as the champions extended their lead at the top of the table.
McCoist said: "It is a fantastic achievement for the players.People will look at the opposition and say this, that and the next thing, but as we have seen this year in cup competitions, the teams from the lower leagues are more than capable of winning games against teams with supposedly better squads.
"It is a great achievement, the boys have got the credit they deserve from ourselves."
Rangers have hit 56 League One goals this term as they have swept their rivals aside with ease in the opening weeks of the season.
Clark doubled his tally for the season with four well-taken strikes and McCoist is delighted for his forward star.
He said: "Nicky works hard at his game. A lot of people, wrongly in my opinion, automatically thought he would just come in [and score] because he got 40 goals last season with Queen of the South. As I have said before, but I don't think everyone believes me, it is a lot harder to score here than people think."