The England international struck again on 73 minutes to put the game beyond the Eagles, but Pulis lamented the lack of concentration from his defender which led to the opening goal.
He told reporters: "Oxlade-Chamberlain has run off the back of Chamakh for the first goal, but Joel Ward's body shape and his position was poor.
"He has held his hands up. If you switch off for a couple of seconds it's a goal."
The North London outfit returned to the summit of the Premier League table with the win, while Palace remain one point clear of the relegation zone.