This dreamy oatmeal creme pie cake turns your favorite childhood snack into a towering layer cake with brown sugar oatmeal cake, marshmallow creme filling, and vanilla buttercream.
I used to rip open oatmeal creme pies from the pantry like they were made of gold, and honestly? Nothing’s changed, except now I turn them into an entire cake. This oatmeal creme pie cake is basically your favorite lunchbox snack all grown up, dressed in marshmallow buttercream and stealing the show at every birthday it attends.
Table of Contents
Why You’ll Love This Oatmeal Creme Pie Cake
This isn’t just a nostalgic snack cake, it’s a full-blown celebration cake that happens to taste like the inside of an oatmeal creme pie. Soft, cinnamon-kissed cake layers meet a fluffy marshmallow filling and a silky vanilla buttercream, then get topped off with crumbled oatmeal creme pies for good measure.
- Soft, spiced brown sugar oatmeal cake layers
- Pillowy marshmallow creme filling in every bite
- Smooth vanilla buttercream frosting that pipes like a dream
- A crunchy, crumbled oatmeal creme pie garnish for texture
It looks like something from a bakery window, but every single step is totally doable in your own kitchen. No fancy equipment required, just a mixer, some patience, and a love of marshmallow creme.
Oatmeal Creme Pie Cake
Equipment
- stand mixer or hand mixer
- Food processor
- Three 6-inch cake pans or two 8-inch cake pans
- Parchment paper
- Baking spray or grease and flour
- mixing bowls
- Whisk
- spatula
- wire rack
- Cake leveler or serrated knife
- Turntable
- piping bags
- Icing smoother
- Wilton 4B piping tip
- Oven
- toothpick
Ingredients
Brown Sugar Oatmeal Cake
- ¾ cup old-fashioned rolled oats 71 g, ground into small pieces; quick oats work too
- 1 ¾ cups sifted cake flour 186 g
- 1 ½ teaspoons baking powder
- ¼ teaspoon baking soda
- 1 teaspoon ground cinnamon
- ½ teaspoon salt
- ½ cup unsalted butter 113 g, room temperature
- 2 tablespoons vegetable oil 30 ml
- ½ cup granulated sugar 100 g
- ½ cup packed brown sugar 100 g; light or dark
- 2 large eggs room temperature
- ¼ cup sour cream 60 g, room temperature
- 2 teaspoons pure vanilla extract
- 1 cup whole milk 240 ml, room temperature
Marshmallow Creme Filling
- ½ cup unsalted butter 113 g, room temperature
- 1 cup powdered sugar 105 g
- 7 ounces Jet-Puffed Marshmallow Creme 198 g; homemade marshmallow fluff can also work
- 1 teaspoon pure vanilla extract
- 1 pinch salt or to taste
Vanilla Buttercream Frosting
- 1 cup unsalted butter 226 g, room temperature
- 3 ½ cups powdered sugar 420 g
- 2 teaspoons pure vanilla extract
- 2 tablespoons whole milk room temperature
- 1 pinch salt or to taste
Garnish
- 2 oatmeal creme pies quartered, for decorating the top
- 2 oatmeal creme pies crumbled, for pressing onto the bottom third of the cake
Optional Variations
- 1 teaspoon ground cinnamon optional, add to vanilla buttercream for cinnamon buttercream
- mini marshmallows optional, fold into marshmallow filling for extra texture
Instructions
- Preheat the oven to 350°F. Prepare three 6-inch cake pans or two 8-inch cake pans with baking spray and parchment circles on the bottoms, or grease and flour the pans.
- Pulse the old-fashioned rolled oats in a food processor until they are broken into small pieces. If using quick oats, they do not need to be pulsed as finely.
- Add the ground oats to a bowl with the sifted cake flour, baking powder, baking soda, cinnamon, and salt. Whisk together and set aside.
- In the bowl of a stand mixer, cream the room-temperature butter on high speed for about 2 minutes, until fluffy.
- Add the vegetable oil, granulated sugar, and packed brown sugar. Mix on medium-high speed for another 2 minutes, then scrape down the bowl.
- With the mixer on low speed, add the eggs one at a time, mixing after each addition.
- Add the sour cream and vanilla extract, then beat on high speed for 1 full minute to help create a soft, tender crumb.
- With the mixer on low speed, add the dry ingredients and mix just until combined. Stream in the milk, then scrape the bowl and finish with a few gentle stirs by hand. The batter should be thick.
- Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes, or until the tops spring back and a toothpick inserted in the center comes out clean.
- Cool the cakes in the pans for 5 minutes, then transfer them to a wire rack to cool completely before frosting.
- Make the marshmallow creme filling. Whip the butter on high speed for about 5 minutes, until smooth, pale, and creamy.
- Turn the mixer to low and add the powdered sugar. Mix for about 2 minutes, until fully combined.
- Add the marshmallow creme, vanilla extract, and salt. Mix on low speed for 1 to 2 minutes, until smooth and uniform.
- Make the vanilla buttercream frosting. Cream the butter on medium-high speed for about 7 minutes, until pale and almost white in color.
- Turn the mixer to low and add the powdered sugar 1 cup at a time, scraping down the bowl between additions so everything incorporates evenly.
- Add the vanilla extract, milk, and salt. Mix on low speed for 1 to 2 minutes, until the buttercream is silky and pipeable.
- Once the cake layers are fully cooled, level and torte them to your desired height if needed.
- Fill a piping bag with about 1 cup of vanilla buttercream and snip a 1/2-inch opening.
- Place the first cake layer on a turntable. Pipe a ring of buttercream around the edge to create a dam, then fill the center with half of the marshmallow creme filling.
- Add the next cake layer and repeat the buttercream dam and marshmallow filling process with the remaining filling.
- Top with the final cake layer upside down so the flat bottom becomes the top. Crumb coat the entire cake with buttercream and chill for at least 20 minutes.
- Use an icing smoother to create a semi-naked finish, then press the crumbled oatmeal creme pies onto the bottom third of the cake.
- Chill the cake for another 10 minutes while loading the remaining buttercream into a piping bag fitted with a Wilton 4B piping tip.
- Pipe swirls around the top edge of the cake, leaving a little space between each swirl. Tuck a quartered oatmeal creme pie between every swirl, then serve.
Notes
Ingredients You’ll Need
This oatmeal creme pie cake comes together in four parts: the cake, the marshmallow filling, the buttercream, and the garnish. Grab everything ahead of time so you’re not digging through the pantry mid-mix.
Brown Sugar Oatmeal Cake
| Ingredient | Amount |
|---|---|
| Old-fashioned rolled oats, ground into small pieces (quick oats work too) | 3/4 cup (71g) |
| Sifted cake flour | 1 3/4 cups (186g) |
| Baking powder | 1 1/2 tsp |
| Baking soda | 1/4 tsp |
| Ground cinnamon | 1 tsp |
| Salt | 1/2 tsp |
| Unsalted butter, room temperature | 1/2 cup (113g) |
| Vegetable oil | 2 tbsp (30ml) |
| Granulated sugar | 1/2 cup (100g) |
| Packed brown sugar (light or dark) | 1/2 cup (100g) |
| Large eggs, room temperature | 2 |
| Sour cream, room temperature | 1/4 cup (60g) |
| Pure vanilla extract | 2 tsp |
| Whole milk, room temperature | 1 cup (240ml) |
Marshmallow Creme Filling
| Ingredient | Amount |
|---|---|
| Unsalted butter, room temperature | 1/2 cup (113g) |
| Powdered sugar | 1 cup (105g) |
| Jet-Puffed Marshmallow Creme | 7 oz (198g) |
| Pure vanilla extract | 1 tsp |
| Salt | pinch, or to taste |
Vanilla Buttercream Frosting
| Ingredient | Amount |
|---|---|
| Unsalted butter, room temperature | 1 cup (226g) |
| Powdered sugar | 3 1/2 cups (420g) |
| Pure vanilla extract | 2 tsp |
| Whole milk, room temperature | 2 tbsp |
| Salt | pinch, or to taste |
Garnish
| Ingredient | Amount |
|---|---|
| Oatmeal Creme Pies, quartered | 2 |
| Oatmeal Creme Pies, crumbled | 2 |
How to Make Oatmeal Creme Pie Cake
This oatmeal cake recipe has a few moving parts, but nothing complicated. Just take it one section at a time and you’ll have a stunning layered oatmeal creme pie cake by the end of the afternoon.
Bake the Brown Sugar Oatmeal Cake Layers
Preheat your oven to 350°F. Prep three 6-inch cake pans or two 8-inch pans with baking spray and a parchment circle on the bottom, or grease and flour them the old-fashioned way.
Pulse the oats in a food processor until they’re broken into small pieces, then dump them into a bowl with the cake flour, baking powder, baking soda, cinnamon, and salt. Whisk it together and set it aside.
Cream the butter in your stand mixer on high for about 2 minutes until it’s nice and fluffy. Add the oil, granulated sugar, and brown sugar, then keep mixing on medium-high for another 2 minutes. Scrape the bowl down.
On low speed, mix in the eggs one at a time. Add the sour cream and vanilla, then crank it up to high and beat for a full minute, this is what gives your cake that soft, tender crumb.
With the mixer still on low, add the dry ingredients until just combined, then stream in the milk. Scrape the bowl and give it a few stirs by hand, the batter will be thick, and that’s exactly what you want.
Quick tip: Don’t overmix once the flour goes in. A few extra stirs by hand beats an extra minute on the mixer every time.
Divide the batter between your pans and bake for 30 to 35 minutes, until the tops spring back and a toothpick comes out clean. Cool in the pans for 5 minutes, then move to a wire rack until they’re completely room temperature before you frost a single thing.
Whip Up the Marshmallow Creme Filling
Whip the butter on high for about 5 minutes until it’s smooth, pale, and creamy. Turn the mixer to low and add the powdered sugar, mixing for about 2 minutes until fully combined.
Add the marshmallow creme, vanilla, and salt, then mix on low until everything’s smooth and uniform, about 1 to 2 minutes. It should look like a cloud you could dive into.
Make the Vanilla Buttercream Frosting
Cream the butter on medium-high for about 7 minutes, until it turns pale and almost white in color. This step matters more than it seems, so don’t rush it.
Turn the mixer to low and add the powdered sugar one cup at a time, scraping down between additions so everything incorporates evenly.
Add the vanilla, milk, and salt, then mix on low for another minute or two until the buttercream is silky and pipeable.
Assemble Your Oatmeal Creme Pie Cake
Once your layers are fully cooled, level and torte them to your desired height. Fill a piping bag with about 1 cup of vanilla buttercream and snip a 1/2 inch opening.
Place your first layer on a turntable and pipe a ring of buttercream around the edge to create a dam. Fill the center with half the marshmallow creme filling.
New to piping fillings? A buttercream dam keeps soft fillings like this one from oozing out the sides, so don’t skip it.
Add your next layer, repeat the dam and fill process with the rest of the marshmallow creme, then top with your final layer upside down so the flat bottom becomes the top. Crumb coat the whole cake and chill for at least 20 minutes.
Use an icing smoother to create a semi-naked finish, then press the crumbled oatmeal creme pies onto the bottom third of the cake. Chill for another 10 minutes while you load the rest of the buttercream into a piping bag fitted with a Wilton 4B piping tip.
Pipe swirls around the top edge, leaving a little space between each one, then tuck a quartered oatmeal creme pie between every swirl. Step back and admire your work, you earned it.
Expert Tips, Variations, and Troubleshooting
Tips for Success
Room temperature ingredients are non-negotiable here, cold butter or eggs will make your batter and buttercream separate or curdle. Set everything out at least an hour before you start baking.
Chilling between each stage, crumb coat included, keeps your layers from sliding and your marshmallow filling from squishing out. It’s the secret to that clean, bakery-style finish.
Fun Variations on This Oatmeal Cake Recipe
Swap the vanilla buttercream for a cinnamon version by adding a teaspoon of cinnamon to the frosting, it plays beautifully with the brown sugar oatmeal cake. You could also fold mini marshmallows into the filling for extra texture.
If you’re craving something a little more low-effort on a weeknight, my viral box cake recipe is a great shortcut when you still want that homemade feel.
And if layered marshmallow desserts are your thing, you’ll probably love my Heaven on Earth cake too.
Troubleshooting Your Layer Cake
If your buttercream looks curdled or soupy, your butter was probably too warm or too cold. Pop the bowl in the fridge for 10 minutes, then keep mixing, it’ll come back together.
If your cake layers sink in the middle, your oven might be running hot or you opened the door too early. An oven thermometer takes the guesswork out of it for next time.
How to Store Your Oatmeal Creme Pie Cake
| Storage Method | How Long It Lasts |
|---|---|
| Room temperature, covered | Up to 1 day |
| Refrigerator, covered | Up to 5 days |
| Freezer, wrapped tightly (whole or by slice) | Up to 2 months |
Because of the marshmallow creme filling and buttercream, this cake keeps best in the fridge. Just let slices sit at room temperature for 20 to 30 minutes before serving so the buttercream softens back up.
To freeze, wrap individual slices tightly in plastic wrap, then foil. Thaw overnight in the fridge before you dig in.
Got extra crumbled cake or trimmed scraps from torting the layers? Don’t toss them, layer them into a jar with leftover buttercream and marshmallow filling for an instant no-waste trifle.
Frequently Asked Questions
Can I use quick oats instead of old-fashioned oats?
Yes, quick oats work fine in this oatmeal creme pie cake and don’t need to be pulsed as finely in the food processor. The texture will be just slightly softer than with old-fashioned oats.
Can I make this oatmeal creme pie cake ahead of time?
Absolutely. Bake the cake layers up to 2 days ahead and store them wrapped at room temperature, or make the whole cake a day ahead and keep it covered in the fridge.
Do I have to use real marshmallow creme, or can I substitute it?
Jet-Puffed Marshmallow Creme gives the filling its classic flavor and texture, and homemade marshmallow fluff can work too, but avoid using melted marshmallows since they set up too firm once cooled.
Can I turn this recipe into cupcakes?
Yes, this batter makes great cupcakes. Fill liners about two-thirds full and bake at 350°F for around 18 to 20 minutes, then fill and frost as you would the layer cake.
Why did my buttercream frosting turn grainy or curdled?
This usually happens when the butter is too cold or too warm. Let it come fully to room temperature before starting, and if it curdles anyway, keep mixing, it almost always smooths back out.
Conclusion
This oatmeal creme pie cake takes everything you love about the lunchbox classic and turns it into a showstopper worth slicing into at any celebration. Soft brown sugar oatmeal cake, that pillowy marshmallow filling, and smooth vanilla buttercream make every bite feel like a little bit of nostalgia.
If you’re in the mood for more marshmallow-loaded desserts, check out my Berry Chantilly cake recipe or the ridiculously simple 4 ingredient yogurt cake for your next baking day.
Give this oatmeal creme pie cake a try, then snap a photo and pin it for later so you can make it again. I’d love to hear how yours turns out in the comments below.
