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Oatmeal Cream Pie Cake

Oatmeal cream pie cake is a tall oatmeal spice layer cake with a thick, pillowy marshmallow cream filling that oozes between moist layers. It’s frosted in smooth vanilla cream and finished with oatmeal cream pie cookie crumbles and a light powdered sugar dusting.
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Prep Time 30 minutes
Cook Time 30 minutes
cooling 1 hour
Total Time 2 hours
Servings: 12 servings
Course: Dessert
Cuisine: American
Calories: 520
Ingredients Equipment Method Notes

Ingredients
  

For the oatmeal cake
  • 2 cup all-purpose flour
  • 1.5 cup rolled oats blended fine
  • 1.5 cup brown sugar packed
  • 2 tsp cinnamon
  • 1 tsp baking soda
  • 1 tsp baking powder
  • 0.5 tsp salt
  • 3 eggs large
  • 1 cup buttermilk
  • 0.5 cup vegetable oil
  • 1 tsp vanilla extract
For the marshmallow cream filling
  • 0.5 cup butter 1 stick, softened
  • 2 cup powdered sugar
  • 1 jar (7 oz) marshmallow fluff
  • 1 tsp vanilla extract
  • 2 tbsp heavy cream
  • 1 oatmeal cream pie cookies crumle, for garnish
  • powdered sugar for dusting

Equipment

  • 2 sheet pan

Method
 

Bake the oatmeal layers
  1. Preheat the oven to 350°F, then grease two 9-inch round pans. Make sure the pan surfaces are well coated for easy release.
  2. Whisk together the all-purpose flour, blended fine rolled oats, brown sugar (packed), cinnamon, baking soda, baking powder, and salt in a bowl. Whisk until the dry mixture looks evenly speckled.
  3. Whisk the eggs, buttermilk, vegetable oil, and vanilla extract in a separate bowl. Stop when the wet ingredients are fully combined.
  4. Combine the wet ingredients with the dry ingredients and mix until smooth. Scrape the sides as needed so no dry streaks remain.
  5. Divide the batter between the prepared pans and bake for 28-32 minutes until a toothpick comes out clean. The tops should look set and spring back lightly.
  6. Cool the cakes completely before filling or frosting. Let them cool on a rack until no warmth remains in the centers.
Make the marshmallow cream filling
  1. Beat the softened butter until fluffy. Beat long enough to lighten the butter’s color and texture.
  2. Add powdered sugar, marshmallow fluff, vanilla extract, and heavy cream, then beat until smooth and spreadable. The filling should hold shape when lifted with the beater.
Assemble and finish
  1. Place one cake layer on a stand and spread the cream filling generously over the top. Add enough to create an even thick layer that can ooze at the edges.
  2. Place the second layer on top and frost the outside with the remaining cream. Smooth the sides for a clean tall finish.
  3. Crumb le oatmeal cream pie cookies over the top for garnish. Add them generously so you see a textured oat-cookie layer.
  4. Dust with powdered sugar and serve. Finish with a light, even snowfall across the top.

Notes

Pro tip: cool the layers fully before assembly so the marshmallow cream stays thick and doesn’t melt or slide. Store in the refrigerator, covered, for up to 4 days; the flavors improve after a few hours. Freeze unfrosted cake layers (wrap tightly) for up to 2 months; thaw overnight in the fridge and assemble fresh. For a lighter option, use reduced-fat butter and half the powdered sugar, expecting a softer filling texture.