Why have tiny oatmeal cream pies when you can have one giant oatmeal cream pie? This massive oatmeal sandwich cookie is baked in two round cake pans with a layer of sweet cream spread in the center. Slice into oatmeal cream pie cookie bars or just pick it up and eat it as one giant cookie…no judgement here. Either way, it will give you all the nostalgia of a classic Little Debbie treat, just 10x bigger!
Tips for making a giant oatmeal cookie
The recipe starts out by making a batch of oatmeal cookie dough. It’s made just like a classic oatmeal cookie dough, but baked in a completely different way. The dough is split in half and spread between two 8″ round cake pans to form two giant cookies. To ensure yours turn out perfectly even with a light golden brown crust, here’s what you need to know:
- Mixing – There are two important steps in the mixing process that ensure the dough bakes evenly with a solid structure. First, cream together the butter and sugar on medium-high speed for at least 2 minutes. The sugar will whip tiny air pockets all throughout the butter, allowing the heat of the oven to easily flow through the entire cookie. Second, mix in the egg and vanilla for another 2 minutes on medium-high speed. This kick starts the emulsification process, allow the egg to bring together the oil and water within the dough. This will provide a stable structure to the cookie.
- Measuring – I say this in every post, and for good reason. It’s the number one reason why most recipes fail, especially for cookies. If there’s too much flour, the cookie will turn out dry and cakey. If you can, measure the flour with a food scale. Otherwise, to ensure you use the exact amount needed, gently spoon the flour into your measuring cup and level if off with a flat edge. If you scoop directly into the flour container, it packs it down into the cup which could leave you with 1/4 cup or more of added flour.
- Baking – Bake the dough in 8″ cake pans that have been properly prepared. Coat the inside with a thin layer of nonstick spray and then place a round sheet of parchment paper at the bottom of each pan. This will allow for easy release and the paper will help hold the cookie together to prevent it from breaking apart.
- Cooling – Allow the cookies to cool completely before removing from the pan, otherwise they may break. Then, place the cookies in the refrigerator to chill completely. Once firm, they’re much easier to stack on top of each other to form your giant oatmeal cream pie.
How to assemble an oatmeal cream pie
Before assembling you should have these two key ingredients ready to go: firm and chilled oatmeal cookies and thick and chilled buttercream. When they’re both chilled, this makes it easy to move around and lift the cookies and it also prevents the buttercream from smooshing out the sides of the giant sandwich cookie.
First, place one of the large cookies upside down on your serving dish. Then, pipe the buttercream on in a single layer, working in a giant swirl moving from the outside of the cookie to the inside. Spread it even if you have any gaps in the buttercream, then place the other cookie right-side up on top.
Gently press the cookie into the buttercream to seal it in place. Now your giant cookie is ready to slice in to bars!
Tips for slicing oatmeal cream pie bars
When slicing, I recommend using a large serrated knife. Saw into the crust edges as these are the toughest parts to cut through. Once you break through, gently saw and slice down the cookie to prevent the buttercream with squishing out.
This is why it’s important to form the cookie with cold buttercream. When it’s cold and firm, it’s very unlikely it will completely smoosh out of the cookie. It may a very tiny bit (like you see in the picture below) but that just adds to the delicious appeal of these cookie bars!
As for the shapes or amount of bars, you can slice into 8 long and skinny bars, or cut it like a pizza. It’s really up to you and how large of a slice you’re craving.
Can these be made gluten free?
I haven’t tested it, but I would recommend swapping the flour with a good quality gluten free baking flour. I recommend this one by Bob’s Red Mill. Just know that it may make your cookies a bit more delicate so handle with care when assembling.
Can I adjust the types of oats used in this recipe?
As always, I recommend making the recipe as written. If you don’t have both types of oats on hand (that being old fashioned and quick oats) you can try using all of one or the other. Just know that I haven’t tested it this way, and I also suspect all old fashioned oats will lead to a chunkier oatmeal cookie and all quick oats will leave you with a bit less of that chewy texture.
How long will these bars keep?
Store the oatmeal cream pie cookie bars in an air tight container in the refrigerator. They will keep for up to 5-6 days. I recommend consuming at room temperature, so leave the bars out for about an hour before eating. Just make sure to slice into the bars while they’re still cold so that each layer stays in tact.
For more cookie bar recipes, check out my:
- Almond Chocolate Chip Cookie Bars (GF, DF, Vo, RSFo)
- Toasted Marshmallow Peanut Butter Cookie Bars
- Chocolate Chip Cookie Butter Bars
- Healthy Brownie Cookie Dough Bars (GF, V, RSF)
Make sure to tag me @butternutbakery on Instagram and comment below if you make these Oatmeal Cream Pie Cookie Bars. To pin this recipe and save it for later, you can use the button on the recipe card or on any of the photos above. Happy baking!Print
Oatmeal Cream Pie Cookie Bars
- Total Time: 50 minutes + 1 hour cooling
- Yield: 8-10 bars
These oatmeal cream pie cookie bars are like slicing into a giant oatmeal cream pie. Two layers of soft and chewy oat cookie are sandwiched with sweet buttercream.
- 1/2 cup (110g) unsalted butter, room temp
- 1/2 cup (100g) light brown sugar, tightly packed
- 1/4 cup (50g) granulated sugar
- 1 large egg, room temp
- 1 tsp vanilla extract
- 1/2 cup + 2 tbsp (80g) all purpose flour
- 1 tbsp cornstarch
- 1 cup (100g) old fashioned rolled oats
- 1/2 cup (50g) quick oats
- 1/2 tsp baking soda
- 1/2 tsp cinnamon
- 1/2 tsp salt
- 1/2 cup (110g) unsalted butter, room temp
- 1/2 cup (100g) vegetable shortening
- 4–5 cups powdered sugar
- 2–3 tbsp milk
- Preheat the oven to 350F and prepare 2 8″ round cake pans*. Coat the inside with a layer of nonstick spray and place a round sheet of parchment paper on the bottom of each pan.
- In a medium bowl, whisk together the flour, cornstarch, oats, baking soda, cinnamon, and salt. Set aside.
- In a large bowl using a hand or stand mixer with the paddle attachment, cream together the butter and sugars until light and fluffy (about 2 minutes on medium-high speed).
- Add in the egg and vanilla and mix on medium-high speed again for about 2 minutes.
- Mix in the dry ingredients in two parts to not overwhelm the batter. Mix JUST until all of the ingredients are combined. Do not over mix.
- Split the dough between the two pans and spread it even.
- Bake at for 20-22 minutes or until the edges are a light golden brown.
- Place the pans on a cooling rack and allow the cookies to cool for at least 30 minutes, or until the pans are no longer warm to the touch.
- Run a knife around the edge of each cookie, turn them out onto your wire cooling rack and place the cookies in the refrigerator to chill firm (about 45 minutes). This will make it easier during the assembly process.
- While the cookies chill, make the buttercream.
- In a bowl using a hand or stand mixer with the whisk attachment, mix the butter and shortening until smooth.
- Mix in the powdered sugar, one cup at a time. As it begins to thicken, mix in the milk 1 tablespoon at a time in between each cup of powdered sugar.
- The buttercream should be fairly thick but easy to spread. Place the buttercream in the refrigerator to chill for about 20 minutes.
- To assemble, place one cookie upside-down and peel back the paper. Place the buttercream in a piping bag fitted with a larger round tip, or in a ziplock bag with a corner snipped off. Pipe the buttercream in an even layer on top of the cookie.
- Place the other cookie right-side up on top of the buttercream, remembering to peel back the paper beforehand!
- By now, the cookies should be cold but soft enough to slice, and the buttercream should still be cold and thick making these bars easy to slice. I recommend using a serrated knife to saw into the firm curst edges before slicing all the way down into the bars. This stops the buttercream from smooshing out the sides.
- Store your oatmeal cream pie bars in the refrigerator but allow to come up to room temp before eating. Enjoy!
BAKING PANS – You can also use 9 inch pans, just keep an eye on the cookies as they may bake a few minutes faster. If you have them, you can also use 2 8″ square baking pans. And although I haven’t tested it, you can try baking the dough in a single layer in a 9×13″ pan and then cut the cookie in half to sandwich the buttercream in the center.
OATS – If you don’t have both types of oats, you can either use all old fashioned or all quick oats, although I recommend the ratio I have in this recipe. All old fashioned will give you a chunkier texture and all quick oats will give you a more smooth texture.
SHORTENING – You can also use all butter if preferred. Vegetable shortening is used to give it that classic oatmeal cream pie filling texture, just like Little Debbie.
- Prep Time: 30 minutes
- Cook Time: 20 minutes
Keywords: oatmeal cream pie, oatmeal cookies, oatmeal cookie bars, oatmeal cream pie cookie bars
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