Combine peanut butter, butter, and sugars; beat with a fork until creamy.
Gradually beat in eggs and vanilla.
Combine dry ingredients and blend into peanut butter mixture.
Spread batter into a greased 9 X 13 pan and sprinkle with chocolate chips.
Place in 350 degree oven for 5 minutes or until chips are melted. Remove pan from oven and run a knife through the batter to marbleize.
Return to oven and bake for 25 minutes.
Not a NESTLÉ®-tested recipe.