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Chewy Monster Cookie Bars (One-Bowl!)

These Chewy Monster Cookie Bars are everything! They’re thick, chewy, and supremely satisfying. Chock full of your favorite goodies, they’re sure to please everyone.


As each fall season comes around, the boys ask to don Halloween costumes that are scary…or at least scarier than what I’ve allowed.

I’ve been the un-fun mama who’s managed to avoid buying any scary suits ever. The Littles have gone from dressing as adorable fluffy lions to famous athletes. This year, I caved a little and got my oldest a sorta-scary gorilla suit. But only because it still had a fluffy body.

I’m all for Halloween treats and chocolates and hanging out with the neighborhood til way past bedtime…but not so much into the monsters thing.

Unless by monsters, we’re talking cookie bars or the Best Brownies 😉


These Chewy Monster Cookie Bars may look all bright and sweet, but make no mistake about ’em…they’re scary good.

Chock full of peanut butter, oats, chocolate, and M&M’s…these Monster Cookie Bars will create some hair-raising thrills of their own.

Put a plate of these delicious bars out on the dessert table and watch them vanish right before your eyes. Young, old, and all ages in between absolutely adore these chewy bars.

For more fun serve them up with these cake pop for kids!


Here’s to monsters of the chocolate variety 😋


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Stacked of Cookie Bars with M&M

Chewy Monster Cookie Bars (One-Bowl!)

5 from 1 vote
These Chewy Monster Cookie Bars will only dirty one bowl, and are scary-delicious! They're thick, chewy, satisfying, and wonderfully chocolatey.
Prep Time: 10 minutes
Cook Time: 20 minutes
Total Time: 30 minutes
Servings: 20
Author: Amy Dong



  • Preheat oven to 350F with rack on lower middle position. Lightly grease a 9x13" glass baking pan; set aside.
  • In the bowl of a stand mixer fitted with paddle attachment, mix together both sugars and eggs on medium speed, until well combined. Add cinnamon, salt, vanilla, peanut butter, and butter; mix until fully incorporated. Using a wooden spatula, stir in the chocolate chips, baking soda, and oats. Stir to combine well. Scrape dough into prepared pan and lightly/evenly press to fill all corners. Lightly press M&M's evenly across top of dough.
  • Bake 20 minutes or just until sides are golden brown. Do not over-bake. Bars will continue to set firmly upon cooling. Cool in pan, on wire rack completely. Cover and chill for ease of cutting. Cut chilled bars into squares and serve.


Baked bars can be wrapped tightly and frozen for 1-2 weeks.

Nutrition (per serving)

Calories: 341kcal | Carbohydrates: 38g | Protein: 7g | Fat: 19g | Saturated Fat: 8g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 7g | Trans Fat: 0.2g | Cholesterol: 27mg | Sodium: 179mg | Potassium: 235mg | Fiber: 3g | Sugar: 25g | Vitamin A: 143IU | Vitamin C: 0.05mg | Calcium: 43mg | Iron: 2mg
Course: Dessert
Cuisine: American

Source: Chew Out Loud

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