Even though it is still 90 degrees here in Muk town, I have all things Halloween on my brain. More so after making these Monster cookie bars. Although they are not considered a traditional Halloween dessert, they can definitely be brought to a Halloween party. I promise no bars will be left at the end of the night!
A gluten free cookie bar all made in one bowl. Each bar is loaded with hand rolled oats, peanut butter, chocolate chips, M&M's, and peanut butter chips. No flour needed! They are super moist and my neighborhood kiddos loved this snack and I even managed to gobble one up after an intense workout this afternoon!

Monster cookies have always been one of my favorite desserts and apparently a midwest thing! After all, I am a sassy midwest girl! According to the authors of the cookie, they get their name because they are Frankenstein's monster of the cookie world and a mashup of different ingredients!
What makes these Monster cookie bars so awesome?
- They are gluten free and contain absolutely no flour and all gluten free oats!
- The entire recipe can be made in one bowl
- This recipe yields 36 monster cookie bars
- Super moist and chewy, perfect for that afternoon snack!

Ingredients
- Hand rolled oats
- Peanut butter: my favorite peanut butter on this planet!
- Unsalted butter: should be room temperature
- Brown sugar: dark or light
- M&M's
- Semi-sweet chocolate chips
- Peanut butter chips
What is the difference between rolled oats and quick oats?
Although both oats can be used in baking, rolled oats are the preferred for baking these monster cookie bars.
Rolled oats are often called large flake oats and create the perfect chewy texture for these bars. They offer a better aroma and more of a nutty flavor.
Quick oats are broken down even further and will not provide as chewy of a texture for the bars, but taste will not be compromised.
How to make monster cookie bars
First, preheat the oven to 350 degrees. Grease a baking sheet with non-stick spray. Set aside.
Second, in a mixing bowl of a stand mixer fitted with a paddle attachment, cream together the eggs and both sugars until combined. Add in the butter, salt, vanilla, and peanut and mix until smooth. Stir in the baking soda until no lumps are seen.
Third, mix in the oats, chocolate chips, peanut butter chips, and M&M's until just combined. Spread batter evenly onto greased baking sheet pressing down firmly.
Lastly, bake for 20-22 minutes or until the edges are golden brown in color. Cool completely. Cut into squares and serve!










Variations and substitutions
- Add in different baking chips such as butterscotch or white chocolate.
- Make this recipe without flour and use both quick and rolled oats.
- Add in cereal or even Reese's pieces.
FAQ's
Seal the cookie bars into a resealable bag to keep them fresher longer! They will last 1 week and can be frozen for up to 3 months.

Monster cookie bars
Equipment
- Stand mixer fitted with paddle attachment
- Large sheet pan
- Mixing bowls
- Measuring cups and spoons
- spatula
- Non-stick spray
Ingredients
Monster cookie bars
- 6 tablespoon unsalted butter room temperature
- 4 large eggs
- 1 cup granulated sugar
- 1½ cup brown sugar
- 1½ cups peanut butter creamy
- 2½ teaspoon baking soda
- 5½ cups rolled oats not quick oats
- 1 cup m&m's
- 1 cup semi-sweet chocolate chips
- ½ cup peanut butter chips
- ½ tablespoon vanilla extract
Instructions
Monster cookie bars
- Preheat oven to 350°. Grease a large baking/cookie sheet with non-stick spray. Set aside.
- In a stand mixer with large mixing bowl fitted with paddle attachment, mix both sugars and eggs together until smooth. Beat in salt, peanut butter, vanilla, and butter until well combined. Add in baking soda and mix until incorporated and not lumpy.
- Add in the M&M's, chocolate chips, peanut butter chips and oats until just combined.
- Spread and layer the batter into a prepared baking sheet, smoothing out the top to have an even layer. Bake for 20-22 minutes or until the edges are light golden brown in color. Allow to cool in pan. Cut and serve when cooled.
Nutrition
Halloween desserts
- Hocus Pocus Candy bark
- Creepy Monster mash whoopi pies
- Frankenstein Brookie cups
- Howl at the moon sugar cookies
Fun fact of the day!
Put two caps and pure vanilla extract in the oven for an hour. Within 20 minutes your house will smell like heaven. I may have to try this one!
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