Gluten Free Monster Cookie Bars
Gluten Free Monster Cookie Bars

Soft and chewy gluten free monstera cookie bars are packed with oatmeal, peanut butter, chocolate chips and M&Ms. Baking them all at once on a sheet will make a whole batch of cookies with a fraction of the effort.

Ever heard of monster cookies? To know her is to love her.

In general, cookies are great for feeding a crowd as one recipe yields dozens, but ladling, shaping, and baking in batches takes time and effort! If you instead spread out your entire bowl of cookie dough on a sheet pan, you can get the job done in one go. Then all you have to do is cut them into squares after baking.

Not only is this recipe a no-brainer for the baker, it’s a dream come true for anyone who gets to eat it. These cookies are soft, chocolatey, and nutty! The rolled oats add great chewiness, the chocolate chips add to the melty, gooey texture, and the M&Ms hold their shape and crunch.

Did I also mention these are gluten free? With all these flavors and textures, you won’t be able to tell the difference.

The best pan for making bar biscuits

For sheet pan cookies we need to use a pan with higher rims that will contain the cookie dough as it rises in the oven and a jelly roll pan is perfect for this. A jelly roll pan is smaller than half a sheet pan; Measures 15×10 inches and has 1 inch taller sides to prevent batter from spilling when baking in the oven.

Top! It’s important to line the pan with parchment paper, leaving an overhang on the two long sides. This way you can easily place the entire sheet pan cookie on a board before cutting into squares. Just make sure you let the cookie cool completely before lifting.

Why Monster Cookies are the Perfect Gluten Free Snack?

Whenever a cookie recipe has multiple elements—nuts, chips, and more—that add to its texture rather than relying primarily on flour, it’s a great candidate for going gluten-free.

In this case, the oats add body and chewy, peanut butter adds creaminess, and the chocolate chips and M&Ms add stickiness and crunch, respectively.

This recipe calls for only one cup of gluten-free flour, and with everything else, no one will miss the gluten. I use King Arthur Measure for Measure Flour, but you can use your favorite gluten-free blend.

Monster Cookie Swaps and Substitutions

There’s more than one way to bake a monster cookie, and you can take this recipe and make it your own. Just make sure the mix-ins stay about 2 cups total.

  • Try half M&Ms and half Reese’s Pieces.
  • Throw in some chopped peanuts!
  • If you have a peanut allergy, swap out peanut butter for almond butter or even sunflower seed butter to avoid nuts altogether. (But stick with creamy or crunchy, and avoid any brands that are 100% natural. Natural nut butters will actually result in a drier cookie.)
  • Try mashed pretzels or potato chips.

A note on oats

This recipe calls for quick cooking of rolled oats because the finer texture helps the cookie dough hold together. If you only have old-fashioned oats, pulse them in a food processor a few times to break them up. Your cookies will have a crumbly texture if you use old-fashioned oatmeal without pulsing it first.

How to save the cookies

Store these gluten free monster cookies in an airtight container at room temperature. They will stay chewy for about 5 days. You can also freeze them between layers of parchment and seal in a ziplock bag for up to 3 months to snack on as needed.

More amazing gluten free treats

  • Gluten Free Chocolate Chip Skillet Cookie
  • Gluten free cinnamon rolls
  • Gluten Free Chocolate Cake Donuts
  • Gluten Free Banana Bread
  • Gluten Free Pumpkin Cupcakes

Gluten-free monster cookie bars

preparation time
10 mins

cooking time
15 minutes

total time
25 minutes

24 biscuit squares

Use your favorite gluten-free all-purpose flour mix and be sure to use gluten-free oats. To prepare this recipe you will need a 15 x 10 x 1 inch jelly roll pan (rimmed baking sheet).


  • 1 Cup All purpose gluten free flour

  • 1 Cup Gluten free oatmeal

  • 1/2 teaspoon Salt

  • 1/2 teaspoon baking soda

  • 1/2 Cup unsalted buttermelted and cooled

  • 1 Cup light brown sugarpacked up

  • 1/2 Cup creamy peanut butter

  • 1 big egg

  • 1 teaspoon vanilla extract

  • 1 Cup M&M’s

  • 1 Cup chocolate chips


  1. Preheat the oven and prepare the baking pan:

    Preheat oven to 350°F. Line the jelly roll pan with parchment paper, leaving a 1-inch overhang on the two long sides. This will later lift the bars out of the pan.

  2. Combine the dry ingredients:

    In a medium bowl, whisk together gluten-free flour, gluten-free rolled oats, salt, and baking soda.

  3. Combine the wet ingredients:

    In a separate large bowl, whisk together the butter, brown sugar, peanut butter, egg, and vanilla until smooth.

  4. Combine the wet and dry ingredients:

    Add the dry ingredients to the bowl with the wet ingredients and stir. Reserve 2 tablespoons each of M&Ms and chocolate chips. Add the rest to the cookie dough and stir

  5. Pour batter into prepared baking pan:

    Invert the dough onto the prepared baking pan. Place a sheet of parchment paper on top and gently press it evenly into the pan with your hands. Remove the top piece of parchment. Scatter the reserved M&Ms and chocolate chips on top, pressing just lightly into the batter

  6. Bake cookie bars:

    Bake the cookie bars until the dough has risen and the edges have just started to turn light golden, 15 to 17 minutes. The center may not appear ready, but it will set as it cools.

  7. Chill the cookie bars:

    Cool in the baking pan on a cooling rack for at least 1 hour.

  8. Cut and serve cookie bars:

    Using the sides of the parchment as a loop, place the sheet pan cookie on a board, cut into 24 bars and serve.

nutritional information (per serving)
207 calories
11g Fat
26g carbohydrates
3g protein
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Hello everybody, Even if you're limited on time and money, I believe you can prepare wonderful food with everyday products. All you have to do is cook cleverly and creatively!