Former NY Giants star OJ Anderson picked up the bar tab for a thirsty group of hockey fans this week -- even though they were rooting against his favorite team in the Stanley Cup Finals ... the L.A. Kings.

It all went down during Game 1 between the Kings and the NJ Devils. OJ hit up Miami Mike's Sports Zone in Jersey to watch the action ... where, of course, he was surrounded by Devils fans.

According to Miami Mike himself, OJ didn't let that stop him from slipping on a hockey glove and cheering loudly for the Kings and his fave player Colin Fraser ... who scored the first goal in the Kings' victory.

MM says OJ -- MVP of Super Bowl XXV -- was in the mood to celebrate the win, and "ordered a round of shots for about 25 guys after the game." We're told the boozefest set OJ back $125, plus he tacked on a fat 40% tip of $50!

See, they're hockey fans too -- football players.