Malfoy certainly did talk about flying a lot. He complained loudly about first years never getting on the house Quidditch teams and told long, boastful stories that always seemed to end with him narrowly escaping Muggles in helicopters. ... ...
I think the noun word 'house' is used to modify 'teams' in this case, otherwise it would have been written as something like: the house of Quidditch teams.
However, I don't know what it means in this context. I guess that the house teams mean the home teams, maybe? What does "the house Quidditch teams" exactly mean?