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A hand lifts a square oat bar topped with chocolate and chopped peanuts from a stack on a tray, with more bars and ingredients visible in the background.
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Lunch Lady Peanut Butter Bars

Thick, soft peanut butter bars topped with rich chocolate frosting. Just like the classic school cafeteria favorite, but even better at home.
Prep Time15 minutes
Cook Time25 minutes
Total Time40 minutes
Course: Dessert
Cuisine: American
Servings: 16 Bars
Calories: 508kcal
Author: Wendy

Equipment

  • 9x13 baking dish
  • mixing bowls
  • hand mixer or stand mixer
  • spatula

Ingredients

For the Peanut Butter Bars:

  • 1 cup unsalted butter softened
  • 1 cup creamy peanut butter
  • 1 cup granulated sugar
  • 1 cup brown sugar
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 2 cups all-purpose flour
  • 1 teaspoon baking soda
  • ½ teaspoon salt

For the Chocolate Frosting:

  • ½ cup unsalted butter softened
  • ¼ cup unsweetened cocoa powder
  • 3 cups powdered sugar
  • ¼ cup milk
  • 1 teaspoon vanilla extract

Instructions

1️⃣ Prep

  • Preheat oven to 350°F.
  • Grease a 9x13 baking dish or line with parchment.

2️⃣ Make the Peanut Butter Base

  • In a large bowl, cream butter, peanut butter, granulated sugar, and brown sugar until light and fluffy.
  • Add eggs and vanilla. Mix well.
  • In a separate bowl, whisk flour, baking soda, and salt.
  • Gradually add dry ingredients to wet ingredients. Mix until just combined.
  • Spread evenly into prepared pan.

3️⃣ Bake

  • Bake 20 to 25 minutes until edges are lightly golden and center is set.
  • Do not overbake. These should stay soft.
  • Let cool completely before frosting.

4️⃣ Make the Frosting

  • Beat butter and cocoa powder until smooth.
  • Add powdered sugar, milk, and vanilla.
  • Beat until creamy and spreadable.
  • Spread evenly over cooled bars.

5️⃣ Slice & Serve

  • Cut into squares and try not to eat three in a row. I’m not judging if you do.

Notes

✨ Optional Twists
  • Sprinkle flaky sea salt on top
  • Add mini chocolate chips to the batter
  • Swap half the frosting for peanut butter frosting
  • Top with chopped peanuts
💡 Make-Ahead Tip
These keep beautifully covered at room temp for 3 to 4 days. They also freeze well.

🔎 Notes

  • Do not overbake. The bars should remain soft.
  • Sprinkle flaky sea salt on top for a sweet-salty twist.
  • Bars can be stored covered at room temperature for 3–4 days.

Nutrition

Serving: 1Serving | Calories: 508kcal | Carbohydrates: 65g | Protein: 7g | Fat: 27g | Saturated Fat: 13g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 9g | Trans Fat: 1g | Cholesterol: 67mg | Sodium: 227mg | Potassium: 166mg | Fiber: 2g | Sugar: 50g | Vitamin A: 568IU | Calcium: 37mg | Iron: 1mg