These Monster Cookie Bars are soft, chewy, and easy to make oatmeal cookie bars loaded with rolled oats, creamy peanut butter, chocolate chips, and M&M’s. A one-bowl recipe that is perfect for parties, gatherings, and more!
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Are you a cookie fan? In my house, we love all cookies! From classic chocolate chip cookies, to peanut butter oatmeal, chocolate brownie, and even macaroon cookies! Yum! This monster bars recipe takes old-fashioned monster cookies and turns them into the ultimate cookie bar! Easier to eat, serves more people, no need to scoop cookie dough, and more! In fact, making cookie bars is my favorite because it really cuts down on prep time since there is no need roll and bake cookies or use multiple baking sheets. Make a batch, spread the cookie dough into the prepared baking pan, and off to the oven it goes!
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What are Monster Cookie Bars?
If you have never had a Monster Cookie before, I am glad you are here! After one bite of this monster bar recipe, you may just fall in love and not look back! Monster Cookie Bars are known for being a thick, chewy, delicious cookie. Due to the oats, they stay thick and the perfect texture! With creamy peanut butter added in, they mimic a peanut butter oatmeal cookie, but even better because they include chocolate chips and M&Ms throughout.
Ingredient Notes for this Monster Cookie Bars Recipe
Using only simple pantry staples, these monster bar cookies come together quickly. See printable recipe card at the bottom of this post for exact recipe ingredient amounts and step by step directions.
- Butter– I use unsalted butter for this recipe since salt is added in as well. Salted butter works great too, just make sure whichever type you use is softened first so it creams together easily.
- Peanut Butter– my favorite is to use creamy, but crunchy works also! Unfortunately, I don’t recommend using natural peanut butter as it changes the taste and texture too much. Stick to Jif, Peter Pan, or Skippy.
- Brown Sugar/ White Granulated Sugar– this adds to the sweetness of the cookie bars. I recommend using light brown sugar instead of dark.
- Eggs– large eggs at room temperature are best as they combine easily into the cookie dough. These help bind everything together.
- Vanilla Extract– try to use pure vanilla versus imitation as it adds so much more flavor!
- Flour– you will want to use all purpose flour. You can also use gluten free flour in this recipe at a 1:1 ratio.
- Oats– you’ll need to use rolled oats as these really add to the texture and keep these chewy. Old Fashioned Oats are the way to go! Make sure you don’t use quick oats!!
- Baking Soda/ Baking Powder/ Salt– make sure these are fresh! I like to change mine out every 6 months to ensure freshness.
- Chocolate Chips– I use semi-sweet chocolate chips, however, feel free to use any flavors desired.
- M&M’s– any flavor works, go classic or feel free to change it up to fit the Holiday or occasion.
Easy Monster Cookie Bars Variations
So many ways to change these up to fit your tastes, the occasion, and more!
- Use different types of chocolate chips! Peanut Butter chips, white chocolate chips, dark chocolate chips, and more all work great!
- Change up the color of the M&M’s to make these bars festive for game day, Valentine’s Day, Christmas, birthdays, and more! Reese’s pieces work great too!
- In place of the M&M’s, you can use Reese’s peanut butter cups, leftover Halloween candy, caramel bits, and anything else you have on hand!
- Serve your cookie bars with a scoop of ice-cream on top for a cookie sundae!
How to make Thick and Chewy Monster Cookie Bars
- Line a 9×9 pan with parchment paper and set aside. Preheat oven to 350° degrees F.
- In a large mixing bowl, cream together the butter, peanut butter, brown sugar and granulated sugar until smooth and creamy.
- Add in the eggs and vanilla extract. Stir until well combined.
- Slowly add in the flour, oats, baking soda, baking powder and salt. Mix until a sticky dough forms.
- Lastly, mix in the chocolate chips and M&M’s.
- Pour the mixture into the prepared baking pan and loosely press/pack the cookie dough into an even layer in the pan.
- Bake in oven for about 25-30 minutes or until the tops are slightly golden brown.
- Allow the cookie bars to cool completely before removing from the pan and cutting into pieces.
Tips for success
- You can also make these in an 8×8 baking pan. If you want a larger amount, simply double the recipe and you can make it in a 9×13 pan. If you choose to make this in a cookie sheet/ sheet pan, you can, just be sure to double the recipe and know that the cookies will be a bit thinner than shown in the pictures. The bake time will decrease slightly.
- Avoid over baking these as they will have a tendency to fall apart and be crumbly if so. Use a toothpick inserted in the center to check if they are done. If the toothpick comes out clean, you can remove. If not, add a minute or two. You want to take these out just before fully baked.
- Use room temperature butter and eggs. This helps everything to combine easily.
Storing Old Fashioned Monster Cookie Bars
- You can make the dough in advance and place in the refrigerator (covered) for up to 48 hours. Let the dough come to room temperature and then press in the pan.
- Store the baked bars in an airtight container at room temperature for up to 4 days.
- You can also freeze the baked cookie bars in a freezer safe container or bag for up to 3 months. Reheat in the microwave before enjoying or allow to thaw to room temperature.
More Cookie Recipes the family will love
Frosted Sugar Cookie Bars– perfect for any occasion and sure to be a crowd pleaser, now you can enjoy all the flavors of classic sugar cookies, without having to chill/roll out the dough.
Ultimate Chocolate Chip Cookie Bars– soft, chewy, and packed with gooey chocolate, these Ultimate Chocolate Chip Cookie Bars are an easy, delicious treat.
Raspberry Chocolate Chip Cookies– soft, chewy, and bursting with the delicious flavors of raspberry and chocolate.
Dark Chocolate Cherry Cookies– soft, flavorful, and simple to prepare, you won’t be able to stop at just one!
Peanut Butter Chocolate Chip Cookies– soft, chewy and combines a basic chocolate chip cookie recipe with a chewy peanut butter cookie!
Chocolate Chip Skillet Cookie– so easy to make and is ready to eat all ooey, gooey and warm straight from the oven!
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Ultimate Monster Cookie Bars
Equipment
Ingredients
- ½ cup butter softened
- ¼ cup peanut butter creamy
- 1 cup brown sugar
- ¼ cup white sugar
- 2 eggs
- 2 teaspoon vanilla extract
- 2 cups flour all purpose
- 1 cup oats old fashioned rolled oats
- 1 teaspoon baking soda
- ½ teaspoon baking powder
- ½ teaspoon salt
- 1 cup chocolate chips any type, I use semi-sweet
- ¾ cup M&M candies
Instructions
- Line a 9×9 pan with parchment paper and set aside. Preheat oven to 350° degrees.
- In a large bowl, cream together the butter, peanut butter, brown sugar, and granulated sugar until smooth and creamy.
- Add the eggs and vanilla. Mix until well combined.
- Add the flour, oats, baking soda, baking powder, and salt. Mix until a sticky dough forms.
- Lastly, mix in the chocolate chips and m&m’s.
- Pour the mixture into the prepared pan and loosely press and pack the dough into the pan.
- Bake at 350° for 25-30 minutes or until the tops are golden brown.
- Allow the cookie bars to cool completely before removing from the pan and cutting.
Nutrition
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