Yields 16 squares


Cookie base

  • 1 1/4 cups (150g) King Arthur Unbleached All-Purpose Flour
  • 1 teaspoon table salt
  • 1/2 teaspoon baking soda
  • 12 tablespoons (170g) unsalted butter, at room temperature
  • 3/4 cup (160g) dark brown sugar or light brown sugar, packed
  • 1/3 cup (66g) granulated sugar
  • 1 1/2 teaspoons cinnamon, preferably Vietnamese
  • 3/4 teaspoon ginger
  • 1 1/2 teaspoons King Arthur Pure Vanilla Extract
  • 2 large eggs
  • 1 3/4 cups (156g) quick-cooking oats or instant oats*
  • *To substitute old-fashioned rolled oats, briefly pulse them in a food processor until each oat is about half its size (several short pulses). 


  • 3/4 cup (138g) vegetable shortening or 8 tablespoons (113g) unsalted butter, softened
  • 3/4 cup (85g) confectioners' sugar
  • 1 cup (128g) Marshmallow Fluff or 1 cup (123g) marshmallow crème, store-bought*
  • 1/2 teaspoon King Arthur Pure Vanilla Extract
  • 1 teaspoon water
  • 1/4 teaspoon table salt
  • Sprinkles, optional


  1. Preheat the oven to 325°F. Lightly grease an 8" square pan and line with a parchment paper sling. 
  2. To make the cookie base: In a medium bowl, whisk together the flour, salt, and baking soda until well-combined.
  3. In a separate large bowl or the bowl of a stand mixer, beat together the butter, sugars, spices, and vanilla, mixing until smooth.
  4. Beat in the eggs one at a time, scraping the bowl between additions, until the mixture is smooth, creamy, and thick.
  5. Stir in the flour mixture until just combined, then mix in the oats. 
  6. Transfer the dough to the prepared pan and smooth it into an even layer with a flexible spatula or an offset spatula.
  7. Bake the oatmeal cream pie bars for 35 to 40 minutes, until the color is a deep golden brown and a toothpick or paring knife inserted into the center comes out clean. Cool for 10 minutes in the pan on the wire rack, then lift out of pan and let cool completely on the wire rack. 
  8. To make the frosting: In a large bowl or the bowl of a stand mixer, beat together the shortening or butter, sugar, and marshmallow until well combined. Add the vanilla, water, and salt and beat until smooth. 
  9. Spread the frosting on top of the cooled bars, top with sprinkles, and slice into 16 pieces. 
  10. Storage information: Store oatmeal cream pie bars in an airtight container at room temperature for up to 3 days. To make ahead, freeze baked (unfrosted) bars, then thaw in the refrigerator overnight. Top with frosting when ready to serve. 


Marshmallow Fluff is a New England ingredient available in certain other parts of the country. Marshmallow creme, more widely available, is a thinner consistency than Fluff. If you make your filling with marshmallow creme, you may need to add a bit more sugar to stiffen it up sufficiently. You can also substitute 1 cup (72g) homemade marshmallow spread if desired. 

For a smaller batch, halve this recipe (preferably by weight) and bake in a 8 1/2” x 4 1/2" loaf pan. 

Recipe courtesy of King Arthur Baking Company