Voldemort was in Slytherin and claimed to be Slytherin while impersonating QQ. The actual QQ was known to be Ravenclaw:

Quirinus... Quirrell," drawled the man now sitting across from where the Defense Professor had waited courteously. The interrogator had tawny hair that swept back like a lion's mane, with yellowish eyes set into the sternly lined face of a man late in his tenth decade. The man was, at this moment, leafing through a large folder of parchments that he had taken from a black and very solid-looking briefcase after he had limped into the room and sat down, seeming not to look at the face of the man he was interrogating. He had not introduced himself.

After some further leafing through parchments, carried out in silence, the Auror spoke again. "Born the 26th of September, 1955, to Quondia Quirrell, of an acknowledged tryst with Lirinus Lumblung..." intoned the Auror. "Sorted into Ravenclaw..."