The European Economic Community, direct predecessor of the European Union, was founded in 1957 by six Western European countries. By the time the EEC chess championship took off the community counted nine member states: West Germany, France, Italy, The Netherlands, Belgium, Luxembourg, United Kingdom, Ireland and Denmark. The biennial event was open for all member countries. Each team had right to field a team of four players and one reserve. The system was a round robin. The United Kingdom had right to put up only one team, although England, Scotland and Wales had independent chess federations enjoying full FIDE membership. As it happened, Scottish and Welsh men played major role in the British teams.

The premier edition was held in Belgium in 1975. All of member countries came to Ostend and Holland won ahead of Denmark. There was a three year gap between first and second event, the latter being held in Teesside (Middlesbrough), England. This one was won by West German team composed of obscure players, very far from level of country's top players like Hübner or Hort. The third edition took part, quite provocatively, in West Berlin in 1980. This one was finally won by Great Britain, who narrowly missed the win in previous events. In late 1980s there were two "Mercato Comune" tournaments organized by Italian Chess Federation - obviously not connected to the official EEC Championships.

That is all that I found in the archives. I have no idea whether other editions were held, but I seriously doubt as there are no signs of it anywhere. It would be nothing strange in cancelling future editions of the event (e.g. due to common financial problems) as it apparently did not manage to gain necessary prestige over the half of a decade of its existence. There were some eminent players there occasionally (rated ca. 2450-2500 Elo, which was European class those years), but it never became one of major European team events comparable to, say, European Team Championship or even Clare Benedicts.

Recent years the individual EU championship started. The inaugural edition took part in Cork, Ireland in 2005. GM Gyimesi of Hungary won ahead of IM Bartel of Poland.