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Oatmeal Cream Pie Cake

Oatmeal cream pie cake is a tall oatmeal spice layer cake with moist crumb and a thick, pillowy marshmallow cream filling that oozes between layers. It’s finished with a smooth vanilla cream frosting and oatmeal cookie crumbles with 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: 430
Ingredients Equipment Method Notes

Ingredients
  

For the oatmeal cake
  • 2 cup all-purpose flour
  • 1.5 cup rolled oats
  • 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 softened (1 stick)
  • 2 cup powdered sugar
  • 1 can (7 oz) marshmallow fluff
  • 1 tsp vanilla extract
  • 2 tbsp heavy cream
  • 1 oatmeal cream pie cookies, crumbled for garnish

Equipment

  • 2 sheet pan
  • 1 stand mixer

Method
 

Bake the oatmeal spice layers
  1. Preheat oven to 350°F and grease two 9-inch round pans. Set aside so the pans are ready for batter.
  2. Whisk together all-purpose flour, blended rolled oats, packed brown sugar, cinnamon, baking soda, baking powder, and salt until evenly combined. Make sure there are no visible flour pockets.
  3. Whisk together eggs, buttermilk, vegetable oil, and vanilla extract in a separate bowl until smooth. The mixture should look uniform and glossy.
  4. Pour wet ingredients into dry ingredients and mix until smooth. Scrape the sides to remove dry streaks.
  5. Divide batter between the pans and bake 28-32 minutes, until a toothpick comes out clean. The tops should spring back lightly when touched.
  6. Cool the cakes completely in the pans, then remove and cool fully again before assembling. This prevents the cream from melting.
Make the marshmallow cream filling and assemble
  1. Beat softened butter until fluffy. Keep mixing until the texture looks paler and airy.
  2. Add powdered sugar, marshmallow fluff, vanilla extract, and heavy cream, then beat until smooth and spreadable. Stop once the filling holds soft peaks.
  3. Place one cake layer on a stand and spread the cream filling generously over the top. Push toward the edges so some cream reaches the perimeter.
  4. Place the second layer on top and frost the outside with the remaining cream. Use a smooth layer so the sides look even.
  5. Crumble oatmeal cream pie cookies over the top for garnish. Sprinkle while the frosting is still fresh so crumbs stick.
  6. Dust with powdered sugar and serve. Slice to show the thick, pillowy filling between layers.

Notes

For clean layers and minimal sliding, cool the cakes fully (room temp) before frosting, ideally after chilling for 1 hour if your kitchen is warm. Store covered in the refrigerator up to 4 days; freeze unfrosted cake layers up to 2 months (wrap tightly). For a lighter option, use light butter and substitute reduced-fat cream in the filling if you’re okay with a slightly softer texture.