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Oatmeal Cream Pie Cake

Oatmeal cream pie cake is a tall oatmeal spice layer cake filled with thick, pillowy marshmallow cream that oozes between moist layers. It’s frosted in smooth vanilla cream and finished with oatmeal 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: 560
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
  • 1 cup buttermilk
  • 0.5 cup vegetable oil
  • 1 tsp vanilla extract
For the marshmallow cream filling
  • 0.5 lb butter, softened
  • 2 cup powdered sugar
  • 1 jar (7 oz) marshmallow fluff
  • 1 tsp vanilla extract
  • 2 tbsp heavy cream
  • oatmeal cream pie cookies, crumbled, for garnish

Equipment

  • 2 sheet pan
  • 1 stand mixer

Method
 

Bake the oatmeal spice cake
  1. Preheat oven to 350°F. Grease two 9-inch round pans.
  2. Whisk together all-purpose flour, blended fine rolled oats, brown sugar, cinnamon, baking soda, baking powder, and salt until evenly combined.
  3. Whisk eggs, buttermilk, vegetable oil, and vanilla extract in a separate bowl until smooth.
  4. Pour the wet ingredients into the dry ingredients and mix until smooth, with no visible flour pockets.
  5. Divide batter between the pans and bake 28–32 minutes, until a toothpick comes out clean.
  6. Cool the cakes completely before assembling so the filling doesn’t melt.
Make the marshmallow cream filling and assemble
  1. Beat softened butter until fluffy, about 1–2 minutes.
  2. Add powdered sugar, marshmallow fluff, vanilla extract, and heavy cream, then beat until smooth and spreadable.
  3. Place one cake layer on a stand and spread the cream filling generously over the top.
  4. Place the second layer on top and frost the outside with the remaining cream.
  5. Crumble oatmeal cream pie cookies over the top for garnish.
  6. Dust with powdered sugar and serve.

Notes

Pro tip: bake the cakes a day ahead and chill them uncovered once cool—cold layers slice and stack cleanly, keeping the marshmallow cream thick and oozing just where you want it. Store assembled cake covered in the refrigerator for up to 4 days; freezing is not recommended for best cream texture. For a lighter swap, use reduced-fat cream cheese frosting-style alternatives aren’t equivalent—best option is to reduce the butter slightly while keeping the marshmallow fluff ratio consistent for stability.