Banana Oatmeal Sheet Cake with Peanut Butter Frosting

Banana Oatmeal Sheet Cake with Peanut Butter Frosting, the ideal recipe to use ripe bananas in and perfect to bring to a party.

A slice of Banana Oatmeal Sheet Cake topped with Creamy Peanut Butter Frosting and chopped peanuts on a small plate next to the remainder of the cake in a baking dish on a cooling rack and a glass of milk and a fork

This Banana Oatmeal Sheet Cake with Peanut Butter Frosting has quickly become my family's favorite cake. It's so easy to make too.

Bananas and peanut butter seem to go well together. A favorite snack of mine is bananas topped with peanut butter so I knew the flavor combination would be perfect.

What Is A Sheet Cake?

A sheet cake is a single-layer cake baked in a flat, rectangular pan called a sheet pan or a jelly roll pan.

Whoever invented the sheet cake is a genius. Sheet cakes are the easiest type of cake to make. They're generally made with pantry staples and no fancy plating is needed since slices are served straight from the pan.

Sheet cakes are also easy to cut, just cut slices as you would brownies or dessert bars and you can decorate them very nicely, as we did with this banana sheet cake.

Ingredient Notes

See recipe box below for ingredient amounts and full recipe instructions.

For the Cake

  • Old-fashioned oats and boiling water: To make oatmeal for the cake.
  • Flour: Use all-purpose flour (plain flour).
  • Baking soda: Gives the cake a little lift.
  • Butter: Softened.
  • Sugar, brown sugar, salt, and vanilla: For flavor.
  • Bananas: 2 bananas peeled and mashed.
  • Eggs: Eggs provide structure in cakes.

For the Frosting

  • Peanut butter
  • Cream cheese
  • Butter
  • Vanilla
  • Heavy cream or milk
  • Powdered sugar

A square slice of Banana Oatmeal Sheet Cake topped with creamy peanut butter frosting and chopped peanuts on a small plate

How To Make This Recipe

  1. Combine the oats and the boiling water and let stand for at least 20 minutes.
  2. Whisk together in a large bowl the flour, baking soda and salt. Set aside.
  3. In a medium bowl, beat the butter and the sugars together at high speed for 3 minutes.
  4. Add in the mashed bananas and beat for 2 minutes more.
  5. Add in the eggs, one at a time beating after each addition.
  6. Mix in the vanilla extract.
  7. Beat in the oat mixture, then the flour mixture. Spoon the batter into the prepared pan and spread evenly.
  8. Bake until a toothpick inserted in the center comes out clean, about 30 minutes.

To Make the Peanut Butter Frosting

  1. In a medium bowl, beat the peanut butter, cream cheese, butter, vanilla and milk together until blended.
  2. Add in 1/3 cup of the powdered sugar and mix. Continue to add in the powdered sugar 1/3 cup at a time until it is all added mix until the frosting is smooth.
  3. If the frosting is too stiff, add additional milk or cream.

Expert Tips

  • Measure the flour by using the spoon and level method. To measure flour correctly, use a spoon to scoop flour into a measuring cup and slightly overfill. Then, use the back of a knife or other straight edged utensil to level the flour across the cup. Do not scoop the flour. When you scoop, the flour gets packed too tightly and you will end up with more flour than the recipe calls for.
  • Do not overmix the cake batter. Mix the ingredients together just until the ingredients are combined. Overmixing causes baked goods to develop a tough texture because you are deflating all the air and over-developing the gluten.

Frequently Asked Questions

How Should I Store This Banana Oatmeal Sheet Cake with Peanut Butter Frosting?

This cake keeps well in the refrigerator for a week.

Can I Freeze Banana Oatmeal Sheet Cake?

Yes! A banana oatmeal sheet cake freezes very well. Cover and freeze the unfrosted cake for two months. Just thaw in the fridge.

A slice of Banana Oatmeal Sheet Cake topped with Creamy Peanut Butter Frosting and chopped peanuts on a small plate next to the remainder of the cake in a baking dish on a cooling rack, a glass of milk, a fork and a bunch of bananas

If you're looking for a mini sheet cake, you can find a Pineapple Mini Sheet Cake and a Mini Texas Sheet Cake as well as many other single serving recipes by visiting our One Dish Kitchen site. 

Enjoy!

Banana Oatmeal Sheet Cake with Peanut Butter Frosting

Moist and delicate Banana Oatmeal Sheet Cake with a rich and fluffy Peanut Butter Frosting.
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Prep Time: 15 minutes
Cook Time: 30 minutes
Servings: 1 13x9-inch cake

Ingredients

  • FOR THE CAKE
  • 1 cup old-fashioned oats
  • 1 1/2 cups boiling water
  • 1 1/3 cup all-purpose flour
  • 1 teaspoon baking soda
  • 1/2 teaspoon salt
  • 1 1/2 tablespoons sticks butter softened, 12
  • 1 cup sugar
  • 1 cup packed brown sugar
  • 2 bananas peeled and mashed
  • 2 large eggs
  • 1 teaspoon vanilla
  • FOR THE FROSTING
  • 1/2 cup smooth peanut butter
  • 4 ounces cream cheese
  • 1 1/2 tablespoons butter
  • 1 teaspoon vanilla
  • 3 tablespoons heavy cream or milk
  • 2 1/2 cups powdered sugar sifted

Instructions

  • Combine the oats and the boiling water and let stand for at least 20 minutes.
  • Preheat the oven to 350 degrees F.
  • Grease a 13x9-inch baking pan.
  • Whisk together in a large bowl the flour, baking soda and salt. Set aside.
  • In a medium bowl, beat the butter and the sugars together at high speed for 3 minutes.
  • Add in the mashed bananas and beat for 2 minutes more.
  • Add in the eggs, one at a time beating after each addition.
  • Mix in the vanilla extract.
  • Beat in the oat mixture, then the flour mixture. Spoon the batter into the prepared pan and spread evenly.
  • Bake until a toothpick inserted in the center comes out clean, about 30 minutes.
  • Let cool.
  • TO MAKE THE PEANUT BUTTER FROSTING
  • In a medium bowl, beat the peanut butter, cream cheese, butter, vanilla and milk together until blended.
  • Add in 1/3 cup of the powdered sugar and mix. Continue to add in the powdered sugar 1/3 cup at a time until it is all added mix until the frosting is smooth.
  • If the frosting is too stiff, add additional milk or cream.

The information shown is an estimate provided by an online nutrition calculator. It should not be considered a substitute for a professional nutritionist’s advice.

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