Old-School Peanut Butter Cookie Bars

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Old-School Peanut Butter Cookie Bars (Lunch Lady Style)

There’s a reason school lunchroom desserts are making a comeback—they're simple, nostalgic, and ridiculously good. These Old-School Peanut Butter Cookie Bars are inspired by the classic lunch lady recipes that once ruled the cafeteria. Rich, soft, and slathered with a warm peanut butter glaze, they’re a one-pan dessert that delivers major comfort food vibes.

Whether you’re baking for a potluck, craving something nostalgic, or just need a foolproof sweet treat, these peanut butter sheet pan bars are your new go-to.

 Why You’ll Love This Recipe

• Sheet pan = no fuss: No scooping or rolling—just spread and bake.
• Bold peanut butter flavor: Both the base and the frosting are loaded with peanut butter.
• Perfect for a crowd: Makes 16–24 bars, ideal for gatherings.
• Freezer-friendly: Bake ahead and freeze for school lunches or snacks.
• Customizable: Add chocolate chips, top with chopped peanuts, or drizzle with chocolate.

 Equipment Needed

• 13x18-inch sheet pan
• Mixing bowls (large and medium)
• Medium saucepan
• Whisk and spatula
• Parchment paper (optional, for easy lifting)
• Cooling rack

Ingredients

For the Bars:

• 2 cups all-purpose flour
• 2 cups granulated sugar
• 1 teaspoon baking soda
• 1 teaspoon salt
• ½ cup whole milk
• 1 teaspoon vanilla extract
• 2 large eggs, beaten
• 1 cup (2 sticks) unsalted butter
• 1 cup creamy peanut butter

For the Glaze:

• ½ cup (1 stick) unsalted butter
• ½ cup creamy peanut butter
• 2 tablespoons milk
• 4 cups powdered sugar

👩‍🍳 Instructions

Step 1: Prep and Preheat

Preheat your oven to 400°F (200°C). Line a 13x18-inch sheet pan with parchment paper or lightly grease it.

Step 2: Mix Dry Ingredients

In a large bowl, whisk together flour, granulated sugar, baking soda, and salt.

Step 3: Prepare Wet Ingredients

In a separate bowl, combine milk, vanilla extract, and beaten eggs. Set aside.

Step 4: Heat Butter and Peanut Butter

In a medium saucepan, melt butter and peanut butter over medium heat until smooth and gently bubbling. Remove from heat.

Step 5: Combine and Mix

Stir the dry ingredients into the warm peanut butter mixture. Then add in the egg-milk mixture and stir until fully combined.

Step 6: Bake

Spread batter evenly into the prepared sheet pan. Bake for 20 minutes, or until a toothpick inserted in the center comes out clean. Let cool completely.

Step 7: Make the Glaze

In a clean saucepan, melt the butter and peanut butter over low heat. Remove from heat and stir in milk. Gradually whisk in the powdered sugar until smooth and glossy.

Step 8: Frost

Pour the warm glaze over the cooled bars. Use a spatula to spread it evenly. Let the glaze set at room temperature.

 Storage Tips

• Countertop: Store covered at room temp for up to 3 days.
• Fridge: Stays fresh for up to a week. Bring to room temp before serving.
• Freezer: Wrap bars individually or as a slab in plastic wrap and freeze for up to 2 months.

 Optional Add-Ons

• Add ½ cup mini chocolate chips to the batter.

• Drizzle the frosted bars with melted chocolate.

• Top with chopped roasted peanuts before the glaze sets for added crunch.

 FAQ

Can I use natural peanut butter?
Yes, but it should be well-stirred and smooth for best texture.

Can I halve this recipe?
Absolutely. Use a 9x13-inch pan and reduce bake time by 2–3 minutes.

Do these taste better the next day?
Even better! The glaze soaks into the bars slightly and softens the texture.

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Old-School Peanut Butter Cookie Bars

Old-School Peanut Butter Cookie Bars (Lunch Lady Style)

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Ingredients Equipment Method Notes

Ingredients

  

For the Bars:

• - 2 cups all-purpose flour
• - 2 cups granulated sugar
• - 1 tsp baking soda
• - 1 tsp salt
• - ½ cup whole milk
• - 1 tsp vanilla extract
• - 2 large eggs beaten
• - 1 cup unsalted butter
• - 1 cup creamy peanut butter

For the Glaze:

• - ½ cup unsalted butter
• - ½ cup creamy peanut butter
• - 2 tbsp milk
• - 4 cups powdered sugar

Equipment

• 13x18-inch sheet pan
• Mixing bowls (large and medium)
• Medium saucepan
• Whisk and spatula
• Parchment paper (optional, for easy lifting)
• cooling rack

Method

 

1. Preheat oven to 400°F (200°C). Line or grease a 13×18-inch sheet pan.
2. Whisk flour, sugar, baking soda, and salt in a large bowl.
3. In a separate bowl, mix milk, vanilla, and beaten eggs.
4. In a saucepan, melt butter and peanut butter until bubbly. Remove from heat.
5. Add dry ingredients to peanut butter mixture. Stir in egg mixture.
6. Spread batter into pan and bake for 20 minutes. Cool completely.
7. For glaze: Melt butter and peanut butter in saucepan. Stir in milk, then powdered sugar until smooth.
8. Pour glaze over cooled bars and spread evenly. Let set before cutting.

Notes

- Store covered at room temp for 3 days or refrigerate up to 7 days.
- Freeze for up to 2 months.

These Lunch Lady Peanut Butter Bars are the kind of dessert that never goes out of style. Moist, sweet, and full of peanut butter flavor, they’re crowd-friendly, nostalgic, and incredibly easy. Bake once, and watch them disappear.