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Oatmeal Cream Pie Cake

Oatmeal Cream Pie Cake with soft spiced oatmeal layers and a thick marshmallow cream filling. Baked in two 9-inch round pans, then stacked and frosted for a classic cream-pie-style slice with cinnamon-sugar style vibes.
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Prep Time 35 minutes
Cook Time 35 minutes
Total Time 1 hour 10 minutes
Servings: 12 servings
Course: Dessert
Cuisine: American
Calories: 430
Ingredients Equipment Method Notes

Ingredients
  

For oatmeal cake layers
  • 2 cup flour
  • 1.5 cup rolled oats
  • 1 tsp baking powder
  • 0.5 tsp baking soda
  • 2 tsp cinnamon
  • 0.5 tsp nutmeg
  • 0.5 tsp salt
  • 1 cup butter
  • 1.5 cup brown sugar
  • 4 eggs
  • 1 cup sour cream
  • 2 tsp vanilla
For marshmallow cream filling
  • 0.5 cup unsalted butter
  • 4 oz cream cheese
  • 7 oz marshmallow creme
  • 2 cup powdered sugar
  • 1 tsp vanilla

Equipment

  • 1 stand mixer
  • 1 sheet pan

Method
 

Bake the oatmeal cake layers
  1. Preheat oven to 350F, then grease two 9-inch round pans and set aside. Aim for fully coated pans so the layers release cleanly.
  2. Beat butter and brown sugar until smooth and lighter in color. Continue mixing as you prepare the next step so the batter stays cohesive.
  3. Add eggs one at a time, then beat until combined. The batter should look thick and glossy after this step.
  4. Mix in sour cream and vanilla until the batter is smooth. Scrape the sides to prevent dry pockets.
  5. Fold in flour, rolled oats, baking powder, baking soda, cinnamon, nutmeg, and salt. Stop mixing once no dry streaks remain and the batter holds together.
  6. Divide batter between the two prepared pans and tap once to level. Keep the layers even for consistent stacking.
  7. Bake at 350F for 30-35 minutes, until a toothpick in the center comes out clean. Watch for lightly browned edges and a set, springy top.
  8. Cool cakes completely in the pans before assembling. This prevents the filling from melting and keeps the crumb stable.
Make and apply the marshmallow cream filling
  1. Beat softened unsalted butter and cream cheese until smooth. Mix until there are no lumps, aiming for a velvety base.
  2. Beat in marshmallow creme until fully incorporated and fluffy. The mixture should look thick and pale with a smooth texture.
  3. Beat in powdered sugar and vanilla until very fluffy and spreadable. Pause to scrape the bowl so the filling stays uniform.
  4. Frost between the cake layers with the marshmallow cream filling. Spread to the edges for a thick, cream-pie feel.
  5. Frost the outside of the cake with any remaining filling. Smooth the top and sides, then let it hold its shape at room temperature.

Notes

Pro tip: cool the cake layers completely before frosting so the marshmallow cream stays thick and doesn’t slip. Store covered in the refrigerator up to 4 days; freeze the unfrosted cake layers up to 2 months (thaw overnight in the fridge), then frost after thawing. For a lighter option, use reduced-fat cream cheese in the filling—texture will still be creamy, though slightly less rich.