Go Back
Chef Ava

Lunch Lady Peanut Butter Bars

These old-fashioned Lunch Lady Peanut Butter Bars bring back memories of school cafeteria treats, with a chewy peanut butter oat base, a creamy peanut butter layer, and rich chocolate frosting. One sheet pan makes 32 bars.
Print Recipe Pin Recipe
Prep Time 20 minutes
Cook Time 15 minutes
Cooling & Setting Time 1 hour 20 minutes
Total Time 1 hour 50 minutes
Servings: 32 bars
Course: Dessert
Cuisine: American
Calories: 371
Ingredients Equipment Method Notes

Ingredients
  

For the Peanut Butter Base
  • 1 cup unsalted butter softened
  • 1 cup granulated sugar
  • 1 cup light brown sugar packed
  • 1 1/2 cups creamy peanut butter
  • 2 large eggs
  • 1 1/2 teaspoons vanilla extract
  • 2 cups all-purpose flour
  • 2 cups old-fashioned rolled oats
  • 1 teaspoon baking soda
  • 1/2 teaspoon salt
For the Peanut Butter Layer
  • 1 1/2 cups creamy peanut butter
For the Chocolate Frosting
  • 1/2 cup unsalted butter softened
  • 3 cups powdered sugar
  • 5 tablespoons unsweetened cocoa powder
  • 1/8 teaspoon salt
  • 1 1/2 teaspoons vanilla extract
  • 4-5 tablespoons whole milk

Equipment

  • 18 × 13-inch baking sheet Line with parchment paper.
  • parchment paper For lining the pan and pressing sticky dough.
  • electric mixer For creaming the butter and beating the frosting.
  • offset spatula For spreading the peanut butter layer and frosting.

Method
 

  1. Preheat the oven to 350°F. Line an 18 × 13-inch baking sheet with parchment paper.
  2. In a large bowl, beat the softened butter, granulated sugar, and brown sugar for 1–2 minutes until light and fluffy.
  3. Mix in 1 1/2 cups peanut butter, eggs, and vanilla until combined.
  4. In a separate bowl, stir together the flour, oats, baking soda, and salt. Gradually add the dry ingredients to the peanut butter mixture, mixing just until combined.
  5. Spread the dough evenly across the prepared baking sheet. If it is sticky, use lightly dampened hands or another piece of parchment paper to press it into place.
  6. Bake for 15 minutes, or until the center no longer looks glossy and the edges are lightly golden. Avoid overbaking so the bars stay chewy.
  7. Remove from the oven and add small spoonfuls of the remaining 1 1/2 cups peanut butter over the warm base. Let it soften for 2–3 minutes, then gently spread into an even layer.
  8. Allow the base to cool completely, about 1–1 1/2 hours, until the peanut butter layer has firmed.
  9. To make the frosting, beat the 1/2 cup softened butter until smooth and fluffy.
  10. Add the powdered sugar, cocoa powder, salt, vanilla, and 4 tablespoons milk. Mix on low until combined, then beat on medium-high for 1–2 minutes. Add the remaining tablespoon of milk if needed for spreading.
  11. Carefully spread the chocolate frosting over the cooled peanut butter layer, leaving a small border around the edges.
  12. Let the frosting set for 20–30 minutes before cutting into 32 bars.

Notes

Avoid overbaking so the bars stay chewy. Let the base cool completely, about 1–1 1/2 hours, before spreading the frosting. Let the frosting set for 20–30 minutes before cutting into 32 bars. Store covered at room temperature for up to 3 days or in the refrigerator for up to 1 week.