Mohsni picked up a second yellow card for kicking the ball at an opponent after play had stopped, resulting in a second red in the space of a month having also been dismissed against Airdrie on January 2.
The 26-year-old will now sit out matches against Ayr United and Stenhousemuir, while he is also just one more yellow card away from receiving another suspension.
"I was very angry and disappointed on Saturday. Bilel knew that and the sending-off was silly and needless. It put us under a little bit of pressure. We had a good chat about it this morning and he's in total agreement with the sending-off, as you would expect. It was a silly thing to do but now we move on," McCoist told the club's official website.
"We don't want it to happen again obviously and hopefully we can learn lessons from that particular incident. Bilel is like Madjid Bougherra was in many ways. They're both really passionate about their football and they react differently when they think an injustice has taken place.
"There was certainly no injustice in the sending-off, though. We just have to direct Bilel's passion and his natural aggression and sometimes he needs to take a step back. If that means counting to 10, he needs to count to 10. As I've said to him today, he's no use to us if he's suspended."
Rangers have dropped just two points in the Scottish League One this season and have a 23-point lead over second-placed Dunfermline Athletic after 23 games.