OnLive, the games-on-demand company that launched last week, said today that it has released the Lego: Harry Potter Years 1-4 video game on its service at the same time the game is being released at retail.

Tonight, OnLive players got to play the game at midnight eastern, before retail stores opened to sell the newest Harry Potter video game for the consoles and the PC. So this is the first game where OnLive has been able to show that it can release brand new titles via its online service at the same time they debut in stores.

Steve Perlman, chief executive of Palo Alto, Calif.-based OnLive, says this kind of release will eventually become the norm as game publishers embrace digital distribution customers at the same time they serve their traditional retail customers. To commemorate the occasion, OnLive staged a contest where the first person to finish the game gets an iPad. The gamers lined up to play the game as soon as it became available. Perlman noted that because the games are stored on servers, there is no way for anyone to cheat.

It’s a small step in the grand scheme of things. But it will be interesting to see what happens if games are released simultaneously in retail and digital channels. By contrast, movie studios still release their DVD movies weeks after the films are available in theaters.