The hit came at the Caps' blueline in the third period, sending the Caps the other way and leading to a Evgeny Kuznetsov go-ahead goal. There was no penalty issued on the play.
An alternate angle shows Oshie lifting up his shoulder/elbow, making contact with Bennett's head.
Bennett popped right back up to his feet on the play, so perhaps that's why the officials thought nothing of the play. I guess the NHL is looking for players to sell illegal hits to make Player Safety's job a little easier.