Peanut Butter Cheerio Bars ingredients: 6 cups Peanut Butter Cheerios 2 Tablespoons butter 1/3 cup smooth peanut butter 10 ounces (approx. 40 ) regular sized marshmallows 1 cup chocolate chips Prep a 9×13 pan with cooking spray or buttered parchment. In a pan over medium high heat melt the butter and peanut butter. Add in the marshmallows until you get a nice gooey mess. Add the Peanut Butter Cheerios and stir to combine making sure all of the cereal gets coated. Press into the prepped pan and while the cereal is still warm, sprinkle the chocolate chips on top so they melt slightly. Let cool and cut into squares. These taste best if served the same day.