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monster cookie bars

Monster Cookie Bars | greens & chocolate

If I had been on top of my game, I would’ve had these monster cookie bars with Easter-colored peanut butter M&M’s posted last week.  Oops.  There were  just so many other yummy things to be posted last week – this frittata, this salad, this flatbread…so. many. yums.  BUT, as you may have noticed – no sweets, and lots of healthy going on.  These bars will fix that!

I made these last week smack dab in the middle of my juice cleanse.  I wasn’t trying to torture myself (though it sure felt like it) but was making them to send to my little brother, who just moved to a new city.  Such a sweet big sister I am.  And modest.  Anyways, these monster cookies which was my second or third post EVER (so um, pardon the photos), are one of his all-time favorite cookies.  They’re, in my opinion, THE BEST monster cookies – thick and chewy, and full of oats, peanut butter,  chocolate chips, butterscotch chips, and M&M’s.  They’re the best, I tell ya.

Howeverrrrr, they do have one fault: one batch makes a lot of cookies which means they take awhile to bake.  With 3 eggs in the recipe, it’s pretty much impossible to cut the recipe in half without some super complicated bakers trick to cut eggs in half, which I’m unaware of.  So, since I was doing my juice cleanse and didn’t want to be rolling out cookies for 2 hours, tempting me even more to shove cookie dough in my face, I turned them into bars.  I also realized as I was adding the oats that I only had 2 cups of oats on hand, and the original recipe calls for 4 1/2 cups, so I switched up the ratio of flour to oats.  My final changes to the original recipe were throwing in some peanut butter chips and using peanut butter M&M’s instead of regular M&M’s because let’s face it, the more peanut butter, the better.

Even though I had to wait 2 days to get a taste of them (I swear monster cookie bars were on the list of recommended things to eat post-cleanse…) they were so worth the wait.  Everything about these are what I love about the monster cookies, except wayyyy easier and faster to make.  Since the recipe for the cookies makes a LOT of cookies, these bars turned out super thick baked in a 9×13″ baking pan.  I love thick bars but if you prefer them a bit thinner, you could definitely make them in a jelly roll pan and just bake them for closer to 20 minutes.

I love that these can be made festive with all of the different season M&M’s.  You could also switch them up and use different kinds of M&M’s.  My favorite is definitely the peanut butter but I think they’d be great with the pretzel or peanut M&M’s too.

Monster Cookie Bars | greens & chocolate

monster cookie bars

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  • 1/2 cup 1 stick unsalted butter, melted
  • 1 cup granulated sugar
  • 1 cup brown sugar
  • 3 large eggs
  • 1 tsp pure vanilla extract
  • 1 tsp corn syrup
  • 1 tsp salt
  • 2 tsp baking soda
  • 1 1/2 cups peanut butter creamy or crunchy, but not natural
  • 2 cups old fashioned oats
  • 2 cups flour
  • 3/4 cup butterscotch chips
  • 3/4 cup chocolate chips
  • 3/4 cup peanut butter chips
  • 1 cup peanut butter M&M's


  • Preheat oven to 325 degrees F.
  • Grease 9x13" baking pan or 10x15" jelly roll pan.
  • In large bowl with electric mixer, beat together butter and sugars with paddle attachment, or using a hand mixer.
  • Add eggs, vanilla, corn syrup, salt, and baking soda and beat until well combined.
  • Add peanut butter and beat until well combined.
  • Add oats and flour and mix until combined.
  • Stir in chips and M&M's by hand. The batter will get pretty thick so use your muscles!
  • Spread evenly into prepared baking pan.
  • Bake in preheated oven for 25-28 minutes if using 9x13" pan or 18-22 minutes for jelly roll pan, until top is golden brown. Don't over bake!
  • Let cool completely.
  • Cut into squares and enjoy!
Tried this recipe?Mention @greensnchocolate to let me know!
Need more ideas?Find all of my recipe pins @greenschocolate

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  1. In the fall I did a juice cleanse for 6 days! How insane is that? I was trying to go for a week, but by day 6 I just couldn’t take it anymore. I had to chew something! How did your 3 days go? Bet it felt great to bite into these delicious cookie bars when you were done : )

    1. After I saw your comment yesterday I headed straight to Target on my lunch break to raid the Easter candy sales…thanks for reminding me! 🙂

  2. I pretty much hate scooping out cookies, so I almost always go the cookie bar route! Plus I think they are just better and chewier that way. 😛 These look AMAZING.

  3. You know I really don’t make cookie bars anywhere near enough! I seem to forget about them I guess! These look amazing – I mean with all the oats, peanut butter chips, chocolate chips….

  4. Love cookie bars – so much faster and easier to get that much needed cookie fix. These look amazing, I love the sound of all the different chips in here – especially the pretty Easter M&M’s 🙂