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Spatula lifting out first square of oatmeal cream pie bars with chewy molasses and oatmeal cookie layer topped with fluffy white marshmallow fluff buttercream and sprinkles.

Oatmeal Cream Pie Bars

These fun cookie bars will remind you of the oatmeal creme pies you used to get in your lunchbox.  They are super easy to make and will give you a taste of childhood!
Prep Time10 minutes
Cook Time30 minutes
Total Time40 minutes
Servings: 24 Servings
Author: Carlee

Ingredients

Molasses Oatmeal Cookie Bars

  • 1 cup butter melted
  • 2 cups light brown sugar packed
  • 4 Tablespoons molasses
  • 1 Tablespoon vanilla extract
  • 2 large eggs
  • 1 teaspoon ground cinnamon
  • ½ teaspoon salt
  • 2 cups instant oats
  • 1½ cups all-purpose flour
  • 1 teaspoon baking powder

Marshmallow Fluff Buttercream

  • 1 cup butter softened
  • 2 cups powdered sugar
  • 1 teaspoon vanilla extract
  • 7 ounces marshmallow fluff
Makes: 10 x 15inch rectangle, 1inch height
US Customary - Metric

Instructions

Oatmeal Cookie Bars

  • Preheat oven to 350°F and grease a 10x15-inch bar pan.
  • Stir together 1 cup butter, 2 cups light brown sugar, 4 Tablespoons molasses, and 1 Tablespoon vanilla extract.
  • Add 2 large eggs and mix well.
  • In another bowl, stir together 1 teaspoon ground cinnamon, ½ teaspoon salt, 2 cups instant oats, 1½ cups all-purpose flour, and 1 teaspoon baking powder.
  • Add dry ingredients to wet ingredients, stirring until just combined.
  • Spread in prepared pan and bake for 25-30 minutes or until set.
  • Allow to cool completely before frosting.

Marshmallow Fluff Buttercream

  • In mixing bowl, beat 1 cup butter until light and fluffy.
  • Add 2 cups powdered sugar, 1 teaspoon vanilla extract, and 7 ounces marshmallow fluff. Mix on medium speed for 4 minutes.
  • Spread over cooled bars. Decorate with sprinkles if desired.
  • Cut into squares and enjoy.

Notes

  • These cookie bars can be stored at room temperature for a couple of days.  They are at their chewy best when stored at room temperature.
  • For longer storage, refrigerate in an airtight container for up to a week.  Or freeze them for up to three months.
  • If you chill them until the frosting is set, you can stack them for storage.  But I would but them in a single layer before you bring them back to room temperature.

Nutrition

Serving: 1Serving | Calories: 341kcal | Carbohydrates: 48g | Protein: 3g | Fat: 16g | Saturated Fat: 10g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 1g | Cholesterol: 56mg | Sodium: 201mg | Potassium: 117mg | Fiber: 1g | Sugar: 35g | Vitamin A: 495IU | Vitamin C: 0.003mg | Calcium: 44mg | Iron: 1mg
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