Peanut Butter Swirl Bars have been some of our favorite brownies for decades. This vintage recipe is so quick and easy to make, plus it uses two of your favorite ingredients. Chocolate and Peanut Butter! This one has a crunchy peanut butter dough and softened chocolate chips swirled gently into the batter to marbleize. These bars are perfect for tailgating parties, potlucks, soccer or gymnastics practice or even holiday baking. No one ever turns these brownies down!