Monster Cookie Bars

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Monster Cookie Bars have all the peanut buttery, chocolatey, chewy goodness of the traditional cookie, only in super easy bar form. 

Monster Cookie Bars - Classic Cookies in easy bar recipe form.

I have a well-established love of bars and bar cookies.

From Peanut Butter Cookie Bars to Apple Blondies, Brownies to fruit-filled Pie Bars, and oh my heart and happy taste buds, Cheesecake Bars too – they all make me happy both because they’re absolutely delicious and they’re so very easy to make!

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Salty sweet graham cracker toffee is perfect for snacking on its own or crumbling over ice cream.

Bars are so much easier and quicker to make than cookies. Cookies can be finicky; they need perfect ratios of flour, sugar, and butter, or they will spread flat or won’t spread at all.

With bars, there is a lot more leeway. With sides on a pan, the dough can’t go anywhere, not to mention it saves all the time rolling, and chilling, and baking individual cookie sheets of dough.

Monster Cookie Bars

These are just perfect for an afternoon snack with a cold glass of milk. And luckily, it only takes a few minutes to stir a batch together.

My boys absolutely love these and they’ve become a serious favorite over the years.

One hour max start to finish, even if you have to Google how to crack an egg first. What excuse do you have for not making them?

Monster Cookie Bars are a kid favorite

These soft and chewy monster bars are easy to make!

Simply cream the butter and sugars together, beat in peanut butter, eggs, and vanilla and stir in the dry ingredients.

Last of all, you’ll fold in some chocolate chips and M&Ms. Press the monster cookie dough into a 9 x 13 pan and bake.

As hard as it is to wait, try to let them cool completely before slicing them into bars.

Monster Cookie Bars - Classic Cookies in easy bar recipe form.

For a few more chocolate and oatmeal dessert combinations to try, don’t miss these Cranberry White Chocolate Oatmeal Cookies and the Chocolate Revel Bars.

These Double Decker M&M Brownies from Whisking Up Yum are calling my name now too!

Monster Cookie Bars - Classic Cookies in easy bar recipe form.

Monster Cookie Bars

4.34 from 12 votes
These monster cookie bars have all the peanut buttery, chocolatey, chewy goodness of the traditional cookie, only in super easy bar form.
Prep Time: 15 minutes
Cook Time: 15 minutes
Additional Time: 1 hour
Total Time: 1 hour 30 minutes
Cuisine: American
Servings: 2 dozen bars


  • ½ cup butter softened
  • 1 cup brown sugar
  • ½ cup peanut butter
  • 2 eggs
  • 1 tsp vanilla
  • cup all purpose flour
  • 1 tsp baking soda
  • cup quick cooking oats
  • ¾ cup semi-sweet chocolate chips
  • 1 cup M&Ms


  • Preheat oven to 350 F. Grease a 9 x 13 pan and set aside.
  • In a large bowl, cream together butter and brown sugar. Beat in peanut butter, eggs and vanilla.
  • In a separate bowl, stir together flour, and baking soda. Add to large bowl and stir until combined. Add oats, chocolate chips and M&Ms.
  • Press into greased pan. Add additional M&Ms to the top, if desired, pressing them into the dough slightly.
  • Bake for 14 – 16 minutes or until edges are slightly brown or until toothpick inserted comes out clean. Do not over bake. Let cool a bit before slicing. Letting them cool completely is best. But its almost impossible to wait that long.


I use salted butter to make this recipe. If you prefer to use unsalted butter, you might want to add a pinch of salt to this recipe.


Serving: 1g · Calories: 194kcal · Carbohydrates: 23g · Protein: 3g · Fat: 11g · Saturated Fat: 5g · Polyunsaturated Fat: 4g · Cholesterol: 27mg · Sodium: 220mg · Fiber: 1g · Sugar: 16g
Tried this recipe?Mention @chocolatewithgrace or tag #chocolatewithgrace!

{originally published 8/19/14 – recipe notes and photos updated 1/4/21}

Classic Lemon Bars

Smooth, tangy lemon filling baked on a shortbread crust and dusted with powdered sugar.
Monster Cookie Bars
Monster Cookie Bars are chocolate, peanut butter happiness!

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  1. Ryann says

    Hello, can I omit the peanut butter? Can I replace it with something else. or just leave it out all together?

  2. Sara says

    5 stars
    These bars are delicious! But I almost never have quick oats on hand, do you think regular rolled oats would work as well?

  3. Ana Agundez says

    I followed the directions and all I got was a dry flour mixture. I went over the directions three times and cannot find my mistake.

    • Mary says

      Without being in your kitchen with you, it’s hard to guess what might have gone wrong, Ana. By chance were you scooping and or shaking your flour vs spooning it into the cup and leveling it off? That’s the most common way that too much flour is added to baked goods. (And that may have created a drier dough for the recipe.)

  4. Cari says

    4 stars
    These were good BUT the amount of salt is to much. It almost makes the cookie bars inedible. Next time I will reduce the amount to 1/4 tsp.

    • Mary says

      Oh my goodness, I am so sorry about that, Cari! That was a mistake in the recipe. I typically make these either with salted butter or just add a pinch of salt to the recipe. I switched over my recipe cards a while back and somehow the measurements were messed up. I’m glad they were still edible – albeit too salty!

    • Mary says

      Hi Brooke, I use salted butter to make this recipe. If you prefer to use unsalted butter, you might want to add a pinch of salt to this recipe.

  5. Julie McDonough says

    3 stars
    I made a double batch. I used all natural peanut butter instead of regular peanut butter. The bars were nice and chewy but fairly bland and dry. Felt like they were missing something. I ended up grinding some pink Himalayan sea salt on top to give it a little more depth of flavor.

    • Mary says

      Hi, Julie! If you used all natural peanut butter as a substitute, that’s probably why the bars were dry afterward. All natural peanut butter tends to be slightly thinner and more watery, which can result in slightly drier baked goods. Using Himalayan sea salt sounds like a great idea, though, and I’ll bet it worked well as a substitute. Enjoy the bars, and I hope your next batch turns out better than the first. Happy baking!

    • Mary says

      You should be able to prep these in advance, Kelly. They should keep on the counter for a day or two; I’d recommend refrigerating or freezing beyond then, depending on how far in advance you’re going to prep.

      • Kelly Wiggins says

        I”m making these for Christmas and i freezer my other cookies like a week or two weeks a head of time then i take some out when i need them.