Oatmeal Cream Pie Bars recreate the classic Oatmeal Creme Pie experience: a fluffy marshmallow cream filling sandwiched between two soft, chewy oatmeal cookie layers. These sandwich cookie bars are simple to prepare and perfect when you want the flavor of filled cookies without scooping and baking individual rounds.
Cookie bars are an excellent shortcut when you love cookies but want less fuss. Instead of shaping and baking many individual cookies, you press the dough into pans and bake whole layers at once. This recipe uses two 9×13 pans so you can assemble an entire batch quickly and evenly.
OATMEAL CREAM PIE BARS
Start by preparing the oatmeal cookie dough, which combines quick oats and old-fashioned oats for the best texture. The dough is divided between two parchment-lined 9×13 pans and baked until just golden. Once cooled, a marshmallow cream filling made with marshmallow fluff, butter, powdered sugar, and vanilla is spread over one layer, then the second layer is inverted on top. Chill briefly, slice into bars, and serve.
Ingredients in Oatmeal Cream Pie Bars
OATMEAL COOKIE LAYERS
Butter – Use real butter, softened to room temperature.
Sugars – A combination of brown sugar and granulated sugar gives balance and chew.
Vanilla extract – Choose a good-quality vanilla for best flavor.
Eggs – Two large eggs bind the dough.
Flour – All-purpose flour works well; gluten-free substitutes can be used if needed.
Cinnamon – Adds warmth and enhances the oats.
Salt – A pinch helps highlight the other flavors.
Baking soda – The leavening agent; ensure it is fresh.
Oats – A mix of quick oats and old-fashioned oats gives the best texture.
MARSHMALLOW CREAM FILLING
Butter – Softened real butter. Salted or unsalted will both work.
Powdered sugar – Provides sweetness and a smooth consistency.
Marshmallow cream – Marshmallow fluff gives the filling its light, pillowy texture.
Vanilla extract – Adds depth to the filling.
HOW TO MAKE OATMEAL CREAM PIE BARS
Preheat the oven and line two 9×13 baking dishes with parchment paper, then lightly spray with nonstick cooking spray.
MAKE THE OATMEAL COOKIE LAYERS
Cream the butter, brown sugar, and granulated sugar in a large bowl with a hand mixer until light and fluffy, about 2–3 minutes.
Add the eggs and vanilla, then beat for another 2–3 minutes.
In a separate bowl, whisk together the flour, cinnamon, salt, and baking soda. Add the dry ingredients to the wet mixture and mix until just combined.
Stir in the quick oats and old-fashioned oats until evenly incorporated. Divide the dough evenly between the two prepared pans and press it into the corners using lightly sprayed hands or a spatula.
Bake at 350°F for about 13 minutes, or until the edges are a light golden brown. Remove from the oven and allow the layers to cool completely.
MAKE THE CREAM FILLING
Beat the softened butter until light and creamy. Add the powdered sugar and continue beating until smooth. Mix in the marshmallow cream and vanilla until the filling is uniform and fluffy.
Ensure the cookie layers are completely cool. Lift one layer from its pan using the parchment paper and place it on a tray. Spread the marshmallow filling evenly over that layer. Lift the second layer from its pan, invert it over the filling, and press gently to adhere. Place the assembled bars in the freezer for 1 hour to firm up, then slice into bars and serve.
Oatmeal Cream Pie Bars
TIPS FOR MAKING THE BEST COOKIE BARS
- Do not melt the butter. Use butter softened to room temperature so the dough creams properly.
- Cream the butter and sugars for 2–3 minutes to improve texture and consistency.
- Always preheat the oven for even baking and predictable timing.
- Line pans with parchment paper to make removing the baked layers simple and clean.
- Remove the bars when the edges are lightly golden. Slightly underbaked bars stay soft and chewy.
HOW DO YOU SOFTEN BUTTER?
To soften butter quickly, use the defrost setting on your microwave in short bursts. Leave butter in its wrapper for a small amount or place the needed portion in a microwave-safe bowl. Use the lowest defrost setting for about 20 seconds, then test with a rubber spatula. If it doesn’t indent easily, heat in additional 5–10 second intervals, watching carefully to avoid melting.
How to store Oatmeal Cream Pie Bars?
Store the bars in an airtight container in the refrigerator for up to 4–5 days. They keep best chilled, but many prefer the flavor and texture if they sit at room temperature for 30–45 minutes before serving. They’re still tasty straight from the fridge if you can’t wait.
HOW TO CUT PERFECT COOKIE BARS
The easiest way to cut neat bars is to bake on parchment paper so you can lift the entire layer from the pan before slicing. This recipe requires removing the baked layers to assemble the sandwich, so parchment makes the process tidy and ensures clean, uniform slices.
LIKE COOKIE BARS? HERE ARE SOME FAVORITES
- Strawberry Cheesecake Cookie Bars
- Snickerdoodle Cookie Bars
- Sugar Cookie Bars
- Chocolate Chip Cookie Bars
- No Bake Cookie Bars
- Oatmeal Chocolate Chip Cookie Bars
- Lemon Sugar Cookie Bars
- Swirled Patriotic Cookie Bars
- Fudgy Oatmeal Cookie Bars
- Twix Cookie Bars
- Easy Peanut Caramel Cookie Bars
- Gingerbread Cookie Bars
- Butterscotch Pretzel Cookie Bars
- Reese’s Cookie Bars
- S’mores Cookie Bars
- Oreo Cookie Bars
Oatmeal Cream Pie Bars deliver the nostalgic marshmallow-filled cookie experience in a simple, shareable bar format. Soft oatmeal layers and a creamy marshmallow center make these a crowd-pleasing dessert that’s easier to assemble than individual sandwich cookies.