Monster cookie bars

I love cookies. I don’t think they are my favorite dessert- it’s too hard to choose. But cookies are up there. There are millions of flavors and they are pretty simple to bake. Now, there’s only one thing that can make cookies easier. Baking them into a bar so you don’t have to scoop them. One giant cookie. And monster cookie bars? It’s like all the cookie flavors in one but none of the work. Win win!

Traditional monster cookies are a peanut butter cookie with oats, chocolate chips and m&m’s. They are delicious but I wanted to change it up just a little. So if you love monster cookies you’ll still enjoy these but they will be just a little different. I swapped chocolate chips for white chocolate chips, made the m&m’s mini so it feels like there are more, and added walnuts. I know nuts in cookies are controversial so feel free to exclude them if it’s not your jam.

In addition to these being a cookie bar, they are no chill so you don’t have to wait to bake either. I’m making it so easy for you, let’s get to baking!

Monster Cookie Bars Key Ingredients

  • Peanut Butter – Like pretty much any recipe on my site, you want to use traditional peanut butter like Jif or Skippy in these monster cookie bars as it is much less likely to separate and change the texture of the bake.
  • Old Fashioned Oats – Old fashioned oats will give you that good chew in the cookie. You can use quick oats in a pinch but your cookies texture will be less chewy.
  • White chocolate – Because the cookies already have milk chocolate from the m&m’s we are going to use white chocolate chips to add a different flavor to them. The white chocolate goes really well with the oats and walnuts.

If you’re looking for some more unique cookie flavors, I’d try:

Monster Cookie Bars

Monster Cookie Bars

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Prep: 20 minutes
Bake: 25 minutes
Servings: 16 bars


  • ½ cup Unsalted butter room temperature
  • 67 g Granulated sugar ⅓ cup
  • 100 g Dark brown sugar ½ cup
  • 2 large Eggs room temperature
  • 1 tsp Vanilla
  • 130 g Creamy peanut butter
  • 80 g Old fashioned oats 1 cup
  • 120 g AP Flour 1 cup
  • ½ tsp Baking soda
  • ½ tsp Sea salt
  • 150 g Mini m&m's ¾ cup
  • 125 g White chocolate chips ¾ cup
  • 55 g Chopped walnuts ½ cup


  • In a medium bowl, add flour, salt, and baking soda and whisk together. Set aside.
  • Preheat oven to 350°F. Line a 9×9 inch pan with parchment paper.
  • In a large bowl or the bowl of your stand mixer with paddle attached, beat together butter, granulated and brown sugar for about 2-3 minutes.
  • Add eggs in 1 at a time, combining into the batter well.
  • Add vanilla and peanut butter and incorporate in.
  • Add oats and mix on low until they are well mixed into cookie dough.
  • Add your dry ingredients (flour, salt, baking soda) to your wet and mix in until just combined.
  • Add your m&m's, chocolate chips, and walnuts and stir in with a spatula.
  • Transfer cookie dough to parchment lined pan and smooth into an even layer.
  • Bake your cookie bars on the center rack of your oven for about 25 minutes.
  • Let your cookie bars cool in the pan for about 10 minutes, then use parchment to transfer to a cooling rack. Allow to cool before slicing.
  • Cookie bars can be stored in an airtight container for 3-4 days. Enjoy!

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