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Oatmeal Sandwich Cookies with Fluffy Vanilla Buttercream Frosting will make you weak in the knees they’re so good. I’m not kidding! They’re also very rich. So make the cookies tiny – about a tablespoon of dough per cookie – and you’ll end up with cookies that are two or three bites of heaven.

Oatmeal Sandwich Cookies stacked on a white plate

These oatmeal sandwich cookies have a satisfyingly complex flavor and texture, one that you’ll want to savor. Made with whole grain flour, thick rolled oats, crunchy walnuts, and ample cinnamon. And for the sandwich filling, I went with fluffy vanilla buttercream frosting – my favorite. 

Oatmeal Cookies Ready to Bake

When you make these, I recommend that you make them very small, just one or two bites. They are incredibly rich. I love this 1 tablespoon scoop, it’s perfect for scooping cookie dough and frosting for the middle.

Oatmeal-Sandwich-Cookie-with-Vanilla-Buttercream-Frosting ready to top

This recipe makes about 25 little sandwich cookies. They make a great edible gift, party or holiday treat and they freeze well too!

Oatmeal Sandwich Cookies with Vanilla Bean Buttercream

5 from 3 votes
Prep: 20 minutes
Cook: 10 minutes
Total: 30 minutes
Course: Dessert
Cuisine: American
Calories: 306
Servings: 25 sandwich cookies
If you don’t feel like making the buttercream, the oatmeal cookies are wonderful on their own. You could add chocolate chips or raisins too.


For the Cookies:

  • 2/3 cup unsalted butter at room temperature
  • 1/2 cup granulated sugar
  • 3/4 cup brown sugar packed
  • 1 egg
  • 1 tablespoon vanilla extract
  • 1 tsp white vinegar
  • ½ tsp salt
  • 1 tsp baking powder
  • ½ tsp baking soda
  • 1 tbsp ground cinnamon
  • 1 cup white whole wheat flour 120 g
  • 2 ½ cups old-fashioned oats 240 g
  • ½ cup chopped walnuts 75 g
  • 1 recipe Fluffy Vanilla Buttercream Frosting


For the Oatmeal Cookies:

  • Preheat oven to 350°F.
  • Line a baking sheet with parchment paper.
  • In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon and salt. Set aside.
  • Add butter and sugars to the bowl of a stand mixer fitted with the paddle attachment. Beat at low speed until combined; increase speed and beat until fluffy, 2 to 3 minutes more. Add egg, vanilla and vinegar; beat well, scraping down sides of bowl as needed. Add flour mixture – cover mixer with a kitchen towel to protect your counters from a flour flurry. Start at low speed to stir, then increase to medium and mix until fully combined. Add rolled oats and walnuts; mix just until combined.
  • Scoop dough into walnut sized balls (my favorite cookie scoop) and arrange about 2-inches apart on prepared baking sheet. Bake for 8 to 10 minutes, until golden brown on the edges and still soft in the middle. Let rest a few minutes on baking sheet before transferring to a cooling rack. Repeat process with remaining dough.

To Assemble Oatmeal Sandwich Cookies:


Calories: 306kcal | Carbohydrates: 34g | Protein: 2g | Fat: 18g | Saturated Fat: 10g | Cholesterol: 48mg | Sodium: 175mg | Potassium: 81mg | Fiber: 1g | Sugar: 24g | Vitamin A: 500IU | Calcium: 33mg | Iron: 0.6mg

Nutrition information is automatically calculated, so should only be used as an approximation.

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Recipe Rating


  1. Paolo Coleho says:

    5 stars
    Great Recipe. I Wonder how you make these wonderful recipes.
    Good work for the foodies!

  2. David @ Spiced says:

    I absolutely love Thalia’s blog! She posts the most amazing looking cakes and other sweets. Speaking of amazing, I’m thinking these cookies need to happen ASAP. I love oatmeal cookies, and I love vanilla buttercream…so this one combines 2 of my favorites. 🙂 I’ll take a baker’s dozen today, please!

  3. Ben Maclain says:

    5 stars
    These little cookie sandwiches look fantastic, Marissa! The combo of oats, walnuts, cinnamon, and slightly salter buttercream frosting makes the perfect treat. Well done!

    1. Marissa says:

      Thank you, my friend!

  4. Mary says:

    These look amazing! Why aren’t you across the street from me so I can help you with the clean up? ?

    1. Marissa says:

      I wish you lived across the street, Mary! xo

  5. Dawn - Girl Heart Food says:

    I love sandwich cookies cause it’s like two cookies for one 🙂 !! Oatmeal cookies are a favourite around here so I can definitely see these happening in our kitchen! Pinned! Happy Easter!

    1. Marissa says:

      Yes! Hooray for two-cookies-for-one (and bonus buttercream)! Happy Easter to you!! xo