Preheat oven to 350. Grease a 9x13 baking dish. Combine bar ingredients. Spread into dish. Bake for 22-26 minutes. Let cool completely before frosting.
Whip cream cheese and then add in butter. Beat together and slowly add the vanilla and powdered sugar. Mix until just incorporated. Whip on high for 1-2 minutes once all ingredients have been added.