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Three peanut butter bars with chocolate frosting stacked on a white plate.
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5 from 3 votes

Lunch Lady Peanut Butter Bars

You have the lunch lady to thank for these old school cafeteria-style Peanut Butter Cookie Bars that have a chewy peanut butter oatmeal cookie base and a thin layer of salty-sweet melted peanut butter underneath those rich swirls of chocolate frosting.
Prep Time25 mins
Cook Time15 mins
Cooling Time1 hr
Total Time1 hr 40 mins
Course: Dessert
Cuisine: American
Servings: 24 servings
Calories: 459kcal
Author: Amy Nash

Ingredients

Bars

  • 1 cup salted butter, softened (227g)
  • 1 cup granulated sugar (200g)
  • 1 cup packed light brown sugar (200g)
  • 2 ½ cups creamy peanut butter, divided
  • 2 large eggs
  • 2 teaspoons vanilla extract
  • 2 cups all-purpose flour, scooped & leveled (282g)
  • 2 cups old-fashioned oats
  • 1 teaspoon baking soda
  • 1 teaspoon salt

Frosting

  • ½ cup salted butter, softened (227g)
  • 3 cups powdered sugar
  • 4 Tablespoons cocoa powder
  • ¼ cup milk
  • 2 teaspoons vanilla extract

Instructions

  • Preheat oven to 350°F. Spray a half-sheet baking sheet (13"x18") with baking spray.
  • Beat the butter, granulated sugar, brown sugar, and 1 cup of the peanut butter in a mixer until creamy and light. Add eggs and vanilla extract, then beat again, scraping the bottom and sides of the bowl.
  • Add the flour, oats, baking soda, and salt. Mix just until combined. Spread the peanut butter oatmeal cookie dough into the prepared pan with a spatula. Bake for 15-17 minutes until golden brown around the edges and barely set in the middle. Do not overbake.
  • While the peanut butter oatmeal cookie base is still hot, melt the remaining 1 ½ cups of peanut butter in the microwave in a microwave safe bowl for 1 minute, then drizzle over the top of the bars, spreading it into an even layer with a spatula or knife. Let cool completely until the peanut butter has firmed up. This can be sped up by sticking the bars in the fridge.
  • Make the chocolate frosting by beating the butter, powdered sugar, cocoa powder, milk, and vanilla extract in a large bowl until smooth. Spread in an even layer over the cooled bars, then cut into squares.

Video

Notes

  • Storage: Keep your bars covered in an airtight container on the counter for 5-7 days. Some rimmed baking sheets come with a plastic lid that is perfect for just this sort of occasion. Or you can just cover them with plastic wrap once the frosting has dried and firmed up a bit. You can also keep the bars in the fridge and serve them chilled, if you prefer.
  • Freezing: These freeze great for 2-3 months. For easier storage, I recommend slicing and separating the bars, then freezing them individually for an hour to set the frosting. Then you can transfer them to a freezer-safe container and stack them so they don't take up as much space in the freezer.
  • Variation: If you STILL can't get enough peanut butter chocolate action, try chopping up some Reese's peanut butter cups to sprinkle on top. Or sprinkle with some Reese's Pieces or chopped dry roasted peanuts instead.
  • Gluten-free version: You can use a 1-to-1 gluten-free baking flour replacement for the flour in this recipe. Just be careful with your oats since some oats actually do have gluten in them. 
  • Allergy-friendly: If you have a peanut butter allergy, these can be made with cookie butter, almond butter, or sunflower seed butter instead.
Recipe adapted from Six Sisters' Stuff.

Nutrition

Calories: 459kcal | Carbohydrates: 51g | Protein: 10g | Fat: 26g | Saturated Fat: 10g | Polyunsaturated Fat: 5g | Monounsaturated Fat: 10g | Trans Fat: 1g | Cholesterol: 44mg | Sodium: 377mg | Potassium: 248mg | Fiber: 3g | Sugar: 35g | Vitamin A: 378IU | Calcium: 34mg | Iron: 2mg