Gluten Free Peanut Butter Cookie Bars

Recipe Ingredient Notes

Gluten-Free Flour: I have tested this recipe with my own gluten-free flour blend, King Arthur Measure for Measure and Bob’s Red Mill 1-to-1. Both flour blends produced a tender, moist crumb, and exceptional flavor. I am not saying other brands will not work in this recipe. I just have not tested them in this application. Flour blends used to develop this recipe do contain xanthan gum.

Peanut Butter: The key ingredient to making Gluten-Free Peanut Butter Chocolate Chip Cookie Bars is definitely peanut butter. I prefer baking with “conventional” peanut butter such as Jif or Skippy. Conventional peanut butter is made with fully hydrogenated vegetable oils, which help stabilize the peanut butter and prevent it from separating. In my opinion, it’s more reliable in baking than natural peanut butter (which is perfect for snacking!). Creamy peanut butter or crunchy peanut butter will work in this recipe.

Brown Sugar: The brown sugar used in this recipe gives them a darker, richer flavor due to the molasses. The flavor is very similar to Toffee. You can use either dark or light brown sugar.

Step by Step Instructions

This recipe for gluten-free peanut butter bars comes together in less than 15 minutes. All you need are a small sauce pan or microwave-safe bowl to melt the butter, a large bowl, and a standard loaf pan. You will also need a flexible rubber spatula and a whisk. No need to bring out the stand mixer.

1. Preheat your oven to 350F and arrange the wire rack in the oven in the middle. Line a standard loaf pan (8.5 x 4.5 inches) with parchment paper. Make sure to leave some overhang on the sides of the pan to remove the peanut butter bars without any issues once baked and fully cooled. (If you use little binder clips to keep parchment paper in place while assembling your peanut butter cookie bars, please remove them before baking!)
2. In a small pot, over medium heat, melt the butter. If you like you can brown the butter which will give the peanut butter bars a rich and nutty note. (Find detailed instructions on how to brown butter here: How to brown butter) Allow the butter to cool for 5 minutes. Alternatively, you can also melt the butter in the microwave.

3. Combine gluten-free flour, baking powder, and kosher salt in a separate medium bowl and set aside.
4. In a large bowl combine the cooled but still fluid butter, peanut butter, vanilla extract, and brown sugar and whisk until smooth. The warmth of the melted butter will help melt the peanut butter.
5. Add the whole egg and whisk until fully incorporated.
6. Once the wet ingredients are fully combined, fold in the dry ingredients using a flexible rubber spatula. This will be easier with a spatula than a whisk.

7. Fold in chocolate chips or other add-ins you may be using (I use Mini Peanut Butter Cups and Dark Chocolate Chips) Add the cookie dough to the prepared pan, smoothing out the top with the back of a spoon or an offset knife in an even layer.
8. Top with additional chocolate if you like and bake at 350F for 23-25 minutes. The gluten-free peanut butter cookie bars are done when the edges are set and golden brown and a toothpick or skewer inserted into the center comes out mostly clean. If you prefer chewy peanut butter cookie bars, make sure to slightly underbake them.
9. Remove the baking dish from the oven, sprinkle with some flaky sea salt if you like, and allow the cookie bars to cool in the pan for about an hour before removing and cutting.

Storage & Freezing

Once cooled, cut the peanut butter cookie bars into individual bars. Then, place them in an airtight container and store them at room temperature for up to 3-4 days.

For longer storage, you can freeze the bars. Place the sliced bars on a sheet tray in the freezer until fully frozen, then transfer them to a freezer-safe container. They can be frozen for up to 3 months. To enjoy, thaw them at room temperature or defrost them in the microwave. They're also great straight from the freezer!

Note about Salt in my Recipes

I use Diamond Kosher Crystal Salt in all of my recipes unless otherwise stated. If use use a different brand or kind of salt in your kitchen please adjust accordingly since some salts can be saltier. If you use Morton’s Kosher Salt please be aware that their salt granules are smaller in size, denser, and crunchier and twice as salty.

Baking in grams

I share my recipes in grams and by weight since baking by weight is the most accurate way to bake. Digital Scales are very affordable and easy to use. You can purchase them on Amazon for less than a set of measuring cups. For small amounts under 10 grams, I like to use this Precision Pocket Scale. Measuring cups are very inaccurate which can cause significant errors when it comes to gluten-free baking or baking in general. Especially since I bake with gluten-free flours which weigh differently than “regular” flours. I do provide some ingredients like spices and leavening agents in measuring spoons. To learn more about Baking with a digital scale, make sure to check out my post about Baking by weight.

Note about Ovens and Oven Temperatures

All my recipes are tested and developed with a conventional oven. I always bake my baked goods on the rack placed in the MIDDLE of my oven. This way the heat coming from the bottom will not burn my baked goods.

If you are baking with convection (fan-forced), please adjust the recipes accordingly. Convection oven can cause baked goods to dry out quickly and still be raw inside. Since takes at least 15-20 minutes for a standard American Oven to be fully preheated. I highly recommend investing in an Oven Thermometer.

Substitutions and Modifications

Any dietary or ingredient modifications/substitutions to this recipe may alter the end result in appearance and taste. I test my recipes several times as published in this post and The Gluten Free Austrian Blog is not responsible for the outcome of any recipe you find on our website.