Preheat oven to 350 degrees.
Spray a 9x13 inch baking dish with non stick cooking spray and set aside.
In a large bowl stir together the yellow cake mix, eggs, melted butter, and vanilla until well combined.
Next, fold in the chocolate chips.
Add the batter to the prepared pan evenly. The batter will be very thick.
Bake in preheated oven for 20-25 minutes, until golden brown around the edges.
Cool completely before cutting.