The case is the latest move by EU antitrust regulators against cross-border curbs on online trade, key to what is seen as a major part of economic growth in the 28-country bloc.
The Commission, which oversees competition policy in the 28 EU countries, said that the companies were Valve Corp, the owner of the world's largest video game distribution platform 'Steam', and five game makers - Bandai Namco, Capcom, Focus Home, Koch Media and ZeniMax.
"In a true digital single market, European consumers should have the right to buy and play video games of their choice regardless of where they live in the EU," European Competition Commissioner Margrethe Vestager said.
The Commission has sent what it calls a "statement of objections" to the companies, allowing them to reply and request hearings to present their arguments.
Companies found guilty of anti-competitive behaviour can be fined up to 10 percent of their annual global turnover.
The Commission said it was concerned that Valve and the five game publishers agreed to prevent cross-border sales by geo-blocking the 'activation keys' that enable consumers to be able to play games.
This may have prevented consumers from buying cheaper games available in other EU countries.
EU antitrust regulators opened its investigation in February 2017, at the same time also looking into online sales of electronics and hotel rooms.
EU rules prohibit geographically based restrictions that undermine online shopping and cross-border sales. Last month, it fined Nike for blocking cross-border sales of soccer merchandise.
(Reporting by Philip Blenkinsop, editing by Louise Heavens)
By Philip Blenkinsop