كتب : Hatem Maher
The title holders will approach El Classico against Barcelona next Sunday in the best possible manner as they enjoy a comfortable lead over the Catalans.
Former Manchester United man Van Nistelrooy broke the deadlock in the 16th minute.
He rose unmarked to head home Sneijder's free-kick from the right, taking his tally to eight goals in the league so far.
Osasuna never troubled the nine-time European champions, who swiftly moved the ball around the pitch.
The penetrating Robinho produced two scares on Osasuna goal as the visitors were totally outplayed.
Sneijder turned from provider to scorer in the 76th minute, collecting a short pass from Van Nistelrooy before firing home from the edge of the area.