Monster Cookie Bars

Quick Summary

Monster Cookie Bars- soft and chewy peanut butter oatmeal cookie bars with chocolate chips and colorful M&M’s. All of your favorites in one pan! The perfect dessert for parties and potlucks!

monster cookie bars

Monster cookies are one of my all-time favorite cookies to bake and eat. I make them all of the time. Well, now I have a new favorite dessert, Monster Cookie Bars. They are basically monster cookies, but in bar form. I adjusted my classic recipe to make a bar cookie and they are fantastic!

I love making the bars when I don’t have time to roll and bake a few dozen cookies. The bars are SO easy and SO fun!

The peanut butter oatmeal cookie bars are soft, chewy, and loaded with chocolate chips and colorful M&M’s. All of the best ingredients in one dessert!

Monster cookie bars are the perfect treat for sharing with family and friends! I love taking them to parties and potlucks because they are easy to make and they are always a crowd pleaser.

monster cookie bars ingredients

You need basic pantry ingredients! These bars are easy to whip up anytime!

  • All-purpose flour– if you need the recipe to be gluten-free, you can use gluten-free flour. I like Cup4Cup or Bob’s Red Mill.
  • Oats– use old fashioned oats, make sure they are gluten-free if you need the recipe to be gluten-free.
  • Baking soda– make sure it is fresh!
  •  Sea salt– a little goes in the bars and a little goes on top!
  • Butter at room temperature!
  • Peanut butter– I don’t recommend natural peanut butter for this recipe. Go with a creamy peanut butter like Skippy or Jif.
  • Sugar– brown sugar and granulated sugar!
  • Eggs– two large eggs to bind everything together.
  • Vanilla extract– yes, it’s one tablespoon! I love vanilla!
  • Chocolate chips– I use semi-sweet, but milk chocolate or dark chocolate will work too!
  • M&M’s– go classic or mix it up for different holidays and use holiday M&M’s. For example, use Christmas M&M’s, Valentine’s Day M&M’s, red, white, and blue M&M’s, etc. You can even use your favorite teams colors and make them for game day!
monster cookie bar dough

Cookie monsters, are you ready to make the most amazing cookie bars? Let’s do it!

  • Preheat the oven and grease a 9×13-inch pan.
  • In a large bowl, whisk together the flour, oats, baking soda, and salt. Set aside.
  • In the bowl of a stand mixer, cream the butter, peanut butter, and sugars together until smooth.
  • Add in the eggs and vanilla and mix until combined.
  • Mix in the dry ingredients, until just combined. Don’t over mix.
  • Stir in the chocolate chips and 1 cup of M&M’s. Grab a spoon and taste the cookie dough. It’s the BEST! And yes, I know you aren’t supposed to eat cookie dough, but I like living on the edge:)
  • Use a spatula to spread the mixture into the prepared pan. Top with the remaining ½ cup of M&M’s.
  • Bake until bars are golden brown and set. Remove the pan from the oven and sprinkle with flaky sea salt. Let the bars cool in the pan before cutting. I know, it’s hard to wait, but let them cool so they can set up. They will be easier to cut.
monster cookie bars recipe

You can make the dough in advance and chill, covered, in the refrigerator 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 on the counter for up to 4 days.

You can also freeze the baked cookie bars in a freezer container or bag for up to 3 months.

easy monster cookie bars

More Bar Desserts

how to make monster cookie bars
Monster Cookie Bars- soft and chewy peanut butter oatmeal cookie bars with chocolate chips and colorful M&M's. All of your favorites in one pan!
5 from 3 votes

Ingredients
  

  • 2 cups all-purpose flour, spooned and leveled
  • 2 cups old fashioned oats
  • 1 teaspoon baking soda
  • 1 teaspoon sea salt
  • 1 cup unsalted butter, at room temperature
  • 1 cup creamy peanut butter
  • 1 1/2 cups packed light brown sugar
  • 1/2 cup granulated sugar
  • 2 large eggs
  • 1 tablespoon vanilla extract
  • 1 1/4 cups semi-sweet chocolate chips
  • 1 1/2 cups M&M’s, divided
  • Flaky sea salt, for sprinkling on bars

Instructions
 

  • Preheat oven to 350 degrees F. Grease a 9×13-inch pan generously with nonstick cooking spray.
  • In a large bowl, whisk together the flour, oats, baking soda, and salt. Set aside.
  • In the bowl of a stand mixer, cream the butter, peanut butter, and sugars together until smooth, about 2 minutes, scraping down the side of the bowl with a spatula, if necessary. Add in the eggs and vanilla and mix until combined.
  • Add the dry ingredients and mix until just combined, don’t over mix.
  • Stir in the chocolate chips and 1 cup of M&M’s.
  • Use a spatula to spread the mixture into the prepared pan. Top with the remaining ½ cup of M&M’s.
  • Bake for 25-35 minutes or until bars are lightly golden brown and set. Don't over bake. You don't want the bars to be dry. Remove the pan from the oven and sprinkle with flaky sea salt. Let the bars cool in the pan. When cool, cut Into bars and serve.

Notes

If you want to make the dough in advance, you can chill the dough for up to 48 hours. Chilling will also soften the oats. 

Nutrition

Calories: 389kcal, Carbohydrates: 46g, Protein: 6g, Fat: 21g, Saturated Fat: 10g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 6g, Trans Fat: 1g, Cholesterol: 36mg, Sodium: 212mg, Potassium: 185mg, Fiber: 3g, Sugar: 30g, Vitamin A: 290IU, Vitamin C: 1mg, Calcium: 46mg, Iron: 2mg

Have you tried this recipe?

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Maria

I'm Maria and my husband is Josh. We share a love of cooking, baking, and entertaining. We enjoy creating recipes that are simple, fresh, and family friendly. We love sitting around the table with good food, good conversation, and good friends and family! Our kitchen is always open!
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  1. 5 stars
    These cookie bars were a big hit. I made them the night before and put them in the oven the next morning before my guests came for lunch. They made the house smell amazing and they were gobbled up in short order. I will be making these again.

  2. 5 stars
    Made these today! Was a hit, everyone enjoyed them! Had to bake for full 45 mins! Very good, love a cookie bar, simple and easy

    1. I am so glad you loved the bars. Every oven is different so I am glad you watched them!

  3. 5 stars
    These were great and were gone in a flash. The only change I made was to do a mix of milk chocolate, semi-sweet chocolate and butterscotch chips. My husband loves butterscotch and it made a nice addition. I will definitely be making these again.