the Eredivisie; the side finished second behind FC Eindhoven and remained in the second tier. In 1975, Groningen established a youth boarding school, and the club tried to rebuild the squad with youth players. The side placed 8th in the 1976–77 Eerste Divisie—Groningen's lowest league finish—before they missed promotion to the Eredivisie on goal difference in the promotion play-offs in 1977–78, despite the 31 goals of Peter Houtman during the season. Groningen finished runners-up to Excelsior in 1978–79, but returned to the Eredivisie as champions in 1979–80 under coach , losing only 4 times in 36 matches. Most of the squad came from Groningen's youth academy. First European matches (1980–1991) In 1982–83, Groningen qualified for European competition for the first time following a 5th-place position. Ronald Koeman left the club in 1983 and joined Ajax, while his brother Erwin remained at Groningen; both players had made their professional debut at Groningen. The team debuted in the 1983–84 UEFA Cup first round with an away match against Atlético Madrid—former European Cup finalists—and lost 2–1. Groningen recorded a 3–0 victory in the return game and won 4–2 on aggregate. Inter Milan were the opponents in the second round; Groningen won 2–0 at their Oosterparkstadion but lost 5–1 in Italy and were eliminated from the competition. Groningen competed in European competition again on five occasions from 1986 until 1992, with a place in the third round in the 1986–87 UEFA Cup (eliminated by Vitória de Guimarães) and the 1988–89 UEFA Cup (eliminated by VfB Stuttgart) as the best results. As a result of the successful spell, Groningen became almost fully professional during the mid-1980s—only Jan van Dijk and Adri van Tiggelen remained semi-professional—and the club recorded the fourth highest average home attendances in Dutch football during this period—behind Ajax, PSV and Feyenoord—as it attracted at least 10,000 fans for each match. In 1989, Groningen reached their first KNVB Cup final but lost 4–1 against PSV. During the same year, Groningen chairman was found guilty by the Fiscal Information and Investigation Service (FIOD) of embezzlement and using dirty money to lure players into signing for the club. De Vries, Groningen's chairman since 1980, stepped down and later spent several days in prison. Although several other clubs were also investigated and punished by the FIOD during this period, Groningen received an additional assessment of 700,000 guilders from the Tax and Customs Administration. The club was