In 1981 Institute joined the Intermediate League. Their first season in the Intermediate league (the 1981–82 season) turned out to be the club's most successful ever in the league. Their first ever intermediate match was a league match against Roe Valley, which they won 8–1. That season they also reached the semi-finals of the Intermediate Cup, where they beat RUC on penalties at the Coleraine Showgrounds, meaning they had earned themselves a place in the first round of the Irish Cup.