Name: Oatmeal Cream Pie Bars
Prep time: 15 min
Cook time: 12 min
Total time: 27 min
Yield: 20 Servings
Cuisine: American

Real Life of Lulu Verified

January 22, 2026

These Oatmeal Cream Pie Bars taste like those classic lunchbox snacks, just bigger, softer, and way more fun. You get chewy oatmeal cookie layers with a fluffy marshmallow filling in the middle that’s hard to resist. They’re super easy to make and even harder to stop snacking on.

From the Cook

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Oatmeal Cream Pie Bars

Real Life of Lulu Verified

Ingredients

WarningMilk and 4 other allergens identified

Instructions

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Instructions

Preheat the oven to 350℉.

Line two 9"x13" baking dishes with parchment paper and spray with nonstick cooking spray. Set aside.

Add 1¼ Cups of butter, brown sugar, and sugar to a large mixing bowl. Beat with a hand mixer until light and creamy.

Add 1 teaspoon of vanilla and eggs and beat until completely combined.

Add the flour, cinnamon, salt, and baking soda to a large mixing bowl and stir.

Add the flour mixture to the brown sugar mixture and beat until everything is mixed together.

Add the quick oats and the old-fashioned oats and beat the mixture again.

Scoop half the mixture into one of the lined 9"x13" baking dishes. Add the other half of the mixture to the other 9"x13" baking dish.

Spray your hands with nonstick cooking spray and flatten the dough with your hands. Spread the dough evenly out to the corners of each dish.

Bake at 350℉ for 13 minutes or until golden brown.

While waiting for the bars to cool, make the cream. Add the ¾ cup butter to a large bowl and beat with a hand mixer until light and creamy.

Add the powdered sugar and beat again until it's completely combined.

Add the marshmallow fluff and 1 teaspoon of vanilla extract and beat again.

The bars must be completely cool before spreading the cream on top. Lift one of the bars out of the dish by lifting the parchment paper up and place the parchment paper lined bar on a tray or sheet pan.

Spread the cream all over the top of the oatmeal bar. Lift the other bar out of the baking dish by the ends of the parchment paper. Carefully flip the bar on top of the cream and lightly press down.

Place in the freezer for at least 1 hour.

Take out of the freezer and slice into bars.

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Tips & Tricks (5)

Room Temperature Magic 🌡️
Ensure all dairy ingredients like butter and eggs are at room temperature to create a smoother, more uniform batter that incorporates more easily and creates a more tender texture.
Oat Blend Perfection 🥣
Mix both old-fashioned and quick oats for the ideal texture - old-fashioned oats provide chewiness while quick oats help bind the cookie layers together more effectively.
Marshmallow Fluff Pro Tip 🍮
Chill the marshmallow filling for 15-20 minutes before spreading to make it easier to handle and create more precise, clean layers in your bars.
Pan Preparation Hack 🧈
Line your baking pan with parchment paper that overhangs the sides, creating easy lift-out handles for cleanly cutting and serving your bars.
Moisture Preservation Trick 💧
Store the bars in an airtight container with a small piece of bread to keep them soft and prevent them from drying out, maintaining that classic soft oatmeal cookie texture.