Soft, chewy cookies sandwich a fluffy homemade marshmallow filling in these Oatmeal Cream Pies. This recipe yields 20 sandwiches in under two hours. Be sure to watch the how-to video for tips!
If you loved Little Debbie’s oatmeal cream pies as a kid, this homemade copycat will bring back those familiar flavors—only better. These sandwiches combine a chewier, softer oatmeal cookie with a cloud-like marshmallow cream filling. The cookies are slightly flatter and less oat-heavy than a traditional oatmeal cookie, which gives the final sandwich the classic texture we all remember.
This version pairs a slightly richer cookie with a homemade marshmallow cream made using a technique similar to Swiss meringue buttercream. It takes some practice to get the filling to perfect stiff peaks, but the result is a light, stable filling that beats store-bought creme. The recipe makes more than a typical boxed pack, so you’ll have plenty to share.
What You Need
These homemade pies avoid preservatives and artificial additives. Key ingredients and why they’re used:
- Unsalted butter: Melted and cooled to create a flatter, softer cookie. Make sure it’s not warm when you combine it with the sugars.
- Sugar: Both dark brown and granulated sugar add chewiness and sweetness.
- Molasses: Adds chewiness and the classic oatmeal cream pie flavor.
- All-purpose flour: Standard base for texture and structure.
- Cornstarch: Keeps cookies soft and tender.
- Cinnamon: A small amount gives the cookies that warm, familiar spice.
- Instant/quick oats: Smaller than rolled oats and blend into the dough for the right texture—not the same as old-fashioned oats.
- Egg whites: Fresh egg whites whip best for the marshmallow filling; carton whites can be unreliable.
- Cream of tartar: Stabilizes the egg whites while whipping.
- Vanilla extract: Essential for the marshmallow filling’s flavor.
RECIPES THAT USE LEFTOVER EGG YOLKS: If you end up with extra yolks, try a pound cake, crème brûlée, lemon curd, or tiramisu—each uses multiple yolks and is a great way to avoid waste.
Scroll down to the recipe card for the full ingredient list and measurements.
How to Make Oatmeal Cream Pies
- Combine melted-and-cooled butter, dark brown sugar, granulated sugar, and molasses. Stir until well mixed, then add eggs and vanilla and stir to combine.
- Whisk together flour, cornstarch, baking soda, cinnamon, and salt. Gradually stir the dry ingredients into the butter mixture until fully combined.
- Stir in instant/quick oats until evenly distributed.
- Drop cookie dough by 1 1/2 tablespoon scoops onto a parchment-lined baking sheet, spacing about 2″ apart. Bake at 350°F (175°C) for about 10 minutes, until edges begin to brown. Cool completely on the baking sheet before assembling.
- Prepare the mixing bowl: Make sure it is completely clean, dry, and grease-free before adding egg whites.
- Bring 1½–2″ of water to a simmer in a saucepan. Place the mixing bowl over the pot (without the bowl touching the water) and whisk egg whites, sugar, cream of tartar, and salt until the sugar dissolves and the mixture reaches 160°F (70°C). To check, rub a small amount between your fingers (careful—it’s hot); there should be no grit.
- Transfer the bowl to a stand mixer and whip with the whisk attachment on medium-high until thick, glossy, and holding stiff peaks, then stir in vanilla. This can take 5–10 minutes with a stand mixer (longer with a hand mixer).
- Assemble sandwiches by scooping about 2 tablespoons of marshmallow cream onto one cookie and pressing a second cookie on top.
SAM’S TIP: If you have a stand mixer, use its metal bowl as the double boiler so you can move it directly from the simmering pot to the mixer. If using a hand mixer, use a heatproof bowl and be prepared for a longer whipping time.
Troubleshooting
Read these tips before you begin to avoid common issues:
- Butter temperature: If melted butter is still warm, it can make the dough greasy and cause cookies to spread too much. Cool the butter completely before mixing with sugars.
- Clean, dry equipment: Even the smallest amount of grease or a bit of yolk will prevent egg whites from whipping properly, so ensure the bowl and whisk are spotless and dry.
- Whip the filling long enough: Whip until the marshmallow cream is thick, glossy, and forms stiff peaks that hold their shape. If peaks fall or fold over, continue whipping.
Frequently Asked Questions
Stored in an airtight container at room temperature, these keep well for about three days. Refrigeration isn’t necessary, but assembled cookies will stay fresher longer if refrigerated. The cookies also soften a bit more the next day, which many people prefer.
Most often that means the butter was still warm when mixed with sugar. Let melted butter cool completely until it’s not warm to the touch before combining.
This recipe uses a homemade vanilla marshmallow cream made from whipped, heated egg whites and sugar. It’s similar in texture to the store-bought filling but lighter and fresher. If you prefer an easier option, see the recipe notes for alternative frosting suggestions.
Let’s bake together! Follow the step-by-step recipe and the video below for details. If you try the recipe, share your results on social media and tag the creator.
Oatmeal Cream Pies
Equipment
- Baking sheet
- Mixing bowls
- Stand mixer or electric hand mixer
- Candy thermometer
Ingredients
For Cookies
- 1 cup (226 g) unsalted butter, melted and cooled
- 1 cup (200 g) dark brown sugar, firmly packed
- ½ cup (100 g) granulated sugar
- 2 Tablespoons unsulphured molasses
- 2 large eggs, room temperature
- 1 ½ teaspoons vanilla extract
- 2 cups (250 g) all-purpose flour
- 2 teaspoons cornstarch
- 1 ¼ teaspoons baking soda
- ¾ teaspoon ground cinnamon
- ¾ teaspoon table salt
- 2 cups (180 g) instant/quick oats
For Marshmallow Cream Filling
- 6 large egg whites (about 210 g)
- 1 ½ cups (300 g) granulated sugar
- ½ teaspoon cream of tartar
- ¼ teaspoon salt
- 1 ½ teaspoons vanilla extract
Instructions
For Cookies
- Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
- Combine melted and cooled butter with both sugars and molasses; stir by hand. Add eggs and vanilla and mix until combined.
- Whisk flour, cornstarch, baking soda, cinnamon, and salt in a separate bowl. Gradually add to wet ingredients and combine.
- Stir in instant oats until fully incorporated.
- Drop dough by level 1½ tablespoon scoops onto prepared baking sheet and bake 10 minutes or until edges are lightly golden. Cool completely on the baking sheet.
For Marshmallow Cream Filling
- Use a double boiler: bring 1½–2″ of water to a simmer in a saucepan. Use a bowl that fits over the pan without touching the water.
- In a clean, dry, grease-free bowl, combine egg whites, granulated sugar, cream of tartar, and salt and whisk to combine.
- Place the bowl over the simmering water and whisk constantly until the sugar dissolves and the mixture reaches at least 160°F (70°C). The mixture should feel smooth when tested between fingers (be cautious—it’s hot).
- Transfer the bowl to a stand mixer and whip on medium-high with the whisk attachment until thick, glossy, and holding stiff peaks (about 5–10 minutes). Stir in vanilla.
Assembly
- Spoon about 2 tablespoons of marshmallow cream onto the bottom of one cookie and top with another cookie to form a sandwich. Serve.
Notes
Other filling options
The marshmallow filling most closely matches classic oatmeal cream pies. For an easier alternative, consider cream cheese frosting, buttercream, or ermine frosting.
Storing
Store assembled cookies at room temperature in an airtight container for up to 3 days. Refrigeration extends shelf life.
Making in advance
Cookies can be baked up to 3 days ahead. Marshmallow cream may be made up to 24 hours in advance; refrigerate and re-whip briefly to restore fluffiness before assembling.
Nutrition
Nutrition information is an approximation.
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