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Oatmeal Cream Pie Cake

Oatmeal Cream Pie Cake is a tender oatmeal spice cake layered with thick, marshmallow-cream frosting. Bake two round layers until set, then frost between layers and on the outside for a classic oatmeal cream pie feel.
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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: 520
Ingredients Equipment Method Notes

Ingredients
  

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
marshmallow cream filling
  • 0.5 cup unsalted butter
  • 4 oz cream cheese
  • 1 can (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 and grease two 9-inch round pans for easy release after baking. Make sure the pans are fully coated so the layers slide out cleanly.
  2. Beat butter and brown sugar until smooth, then add eggs one at a time and mix well. The batter should look thick and creamy with no visible streaks.
  3. Add sour cream and vanilla and beat until the mixture is fully combined and glossy. Scrape the bowl sides to prevent dry pockets.
  4. Fold in flour, rolled oats, baking powder, baking soda, cinnamon, nutmeg, and salt until just combined. Stop as soon as no dry flour remains to avoid tough cake.
  5. Divide the batter evenly between the two pans so layers bake at the same thickness. Tap pans gently to level the tops.
  6. Bake at 350F for 30-35 minutes, until the centers spring back lightly and a toothpick comes out mostly clean. Cool the layers completely in the pans before frosting.
Make and spread the marshmallow cream filling
  1. Beat softened unsalted butter and softened cream cheese until smooth. Stop when the mixture is lump-free and pale.
  2. Add marshmallow creme and beat until fully incorporated. The filling should look thick and uniform.
  3. Beat in powdered sugar and vanilla until very fluffy and spreadable. Visual cue: the frosting holds soft peaks and leaves trails for a moment.
  4. Frost between the layers using a generous layer of filling to sandwich the cakes. Add frosting on the top and then smooth the outside with an even coat.

Notes

For the cleanest slices, cool the cake layers completely before frosting so the marshmallow cream doesn’t loosen or slide. Store covered in the refrigerator for up to 4 days; freezing isn’t recommended for best frosting texture. For a dairy-light option, use reduced-fat cream cheese and butter.