Quick and Easy No Flour Monster Cookie Bar Recipe

5 from 1 vote
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Monster Cookie Bars turn a fully-loaded family-favorite cookie recipe into a dessert that you can make with less than 15 minutes of work and in only one bowl. They are filled with peanut butter, oats, chocolate chips, and M&M candies, but they have no flour. And flourless desserts are naturally gluten free! Get ready to sink your teeth into this perfectly crisp on the outside, gooey on the inside Monster Bar recipe.

One Bowl Monster Cookie Bar Recipe image with title

I’ll be honest, I tend to save my sweets for the weekend. I suppose it’s my way of approaching the 80/20 rule of balancing eating healthy foods and indulging a bit. I’m not going to claim a perfect ratio of 80/20 because this busy mama doesn’t have the time or interest in tracking things that closely. But you know what I’m getting at.

And let’s be real. Yes, sometimes I am testing recipes for the blog. But those aren’t always desserts. So trying to bake something special during the week in the middle of all the craziness that goes along with being a working mom of two school-age boys is next to impossible. 

That is until I received a copy of The Weeknight Dessert Cookbook by Mary Younkin of the popular food blog Barefeet in the Kitchen.

She has created 80 tried and tested surefire recipes that require only five to fifteen minutes of prep time. Sure, some might require some time in the oven, fridge, freezer, or ice cream machine. But after that short timeframe of assembling and combining the ingredients, your work is done.

Just like these bars that are dangerously quick and easy to make. We’ll get back to the book, but let’s first talk about this deliciousness…

The Weeknight Dessert Cookbook with recipe for Monster Cookie Bars
Two Monster Cookie Bars Recipe from The Weeknight Dessert Cookbook

Best Monster Cookie Bar Recipe

Whether you want a quick and easy dessert to treat the family, are looking for something to make quickly to share with friends, want to bake something simple for someone avoiding gluten, or need a recipe for leftover Halloween candy, these no flour cookie bars are perfect.

They are made with basic ingredients, can be mixed together in one bowl in just a few minutes, and bake up fast. And the gooey middle, peanut butter deliciousness, and chocolate overload will make everyone happy.

Ingredients

  • Salted butter – softened to room temperature
  • Light brown sugar
  • White sugar
  • Egg plus egg yolk
  • Vanilla extract
  • Maple syrup
  • Baking soda
  • Crunchy peanut butter
  • Old-fashioned rolled oats – not quick or instant oats
  • Semi-sweet chocolate chips
  • M&M’s candies

Equipment

  • 8-inch square baking pan
  • Parchment paper – to line the pan and make it easier to remove the bars
  • Large bowl – only one bowl to make these bar cookies
  • Hand mixer – you can mix these bars by hand, but a hand mixer will make it easier to blend the butter and sugars together.
  • Large spatula – for mixing in the oats and chocolate chips.
Monster Bars and Milk

Directions

Scroll down to the recipe card for the full instructions, but here is a brief overview just to show you how easy this recipe is. You can totally put everything together in 5 to 15 minutes, just as Mary promises. And keep reading for a few extra tips and tricks.

  1. Preheat your oven to 350°F and line your pan with parchment paper.
  2. Beat the butter and sugars in a large bowl.
  3. Blend in the egg, egg yolk, vanilla, maple syrup, and baking soda.
  4. Stir in the peanut butter, followed by the oats, and then the chocolate chips.
  5. Press the dough into the pan.
  6. Sprinkle the M&M’s on top and lightly press into the dough.
  7. Bake until lightly browned.
  8. Let cool before slicing and store in an airtight container.
One Bowl M&M's Monster Cookie Bars cut into squares

RECIPE PRO TIPS:

Some of these tips are from my experience, and some are directly from Mary, who has tested this recipe multiple times for this cookbook.

  • While it says you can butter your pan well, lining the pan with parchment paper is definitely recommended. Let the parchment overhang the edges by at least an inch, then use the edges to pull the entire thing out at once. This makes it easier to slice the cooled bars on a cutting board.
  • The recipe calls for salted butter. If you only have unsalted butter, just add a pinch of salt.
  • When measuring peanut butter or even something sticky like maple syrup, if you don’t have one of these incredibly useful gadgets, then grease your measuring cup with butter or cooking spray so it slides out easily.
  • Let them cool for at least 15 minutes. There will be some carryover cooking, they will be easier to cut, and you definitely want to store fully cooled bars.
  • Baking for someone avoiding gluten? These are perfect because they are flourless, but if you are dealing with celiac or an allergy, make sure your oats are certified gluten free.
  • Once you have mastered the basic version, try switching it up with different nut butters and candy mix-ins. I might try almond butter and toffee!

No Flour Monster Cookie Squares cut on a piece of parchment paper

Gluten Free Monster Cookie Bars

Gluten Free Disclaimer: I am not a medical professional. This information is solely based on my research and personal experience, and I provide it as a courtesy to my readers. Please consult your doctor or medical professional for any questions as it relates to your needs, particularly if you have celiac disease or a severe gluten allergy or intolerance. Products, manufacturing facilities, and ingredients change frequently, so you should always contact the manufacturer for the latest information. 

Monster Cookies are traditionally a flourless cookie, and this recipe is as well. So no flour monster cookie bars are perfect to make for those that are avoiding gluten. If these are being served to someone with celiac disease or a severe allergy or sensitivity, you’ll want to pay attention to the oats, in particular, and ensure you make them with certified gluten free rolled oats.

Are M&M’s gluten free?

According to the Mars website, wheat, barley, and rye ingredients by name and any wheat cross-contamination risks on the label, but may not declare possible barley or rye cross-contamination. This is recent, so if you have previously eaten M&M’s without issue, you might still want to be cautious.

But regular M&M’s and most of the standard flavors such as Peanut and Almond have no gluten ingredients. Do avoid the Pretzel and Crispy M&M’s, and use caution with special or seasonal flavors, which may be manufactured on lines where there is a risk of cross-contamination.

Best Monster Cookie Bars topped with M&Ms on a plate

The Weeknight Dessert Cookbook

What do I love about this cookbook? I’m already a fan of Mary’s recipes, both from her blog and her cookbooks. Her Barbecue Chicken Tostadas from The Weeknight Dinner Cookbook are on regular rotation in my house. And while we aren’t eggs for breakfast people, we love the Breakfast Tostadas from The Weekday Lunches and Breakfasts Cookbook. So I knew that The Weeknight Dessert Cookbook would be amazing too!

As I mentioned, there are 80 dessert recipes, with a mouthwatering photo of every single decadent treat. And each can be made with only five to fifteen minutes of effort on your part. So these recipes are perfect to treat the kids to something special after school, serve to unexpected company, bring along to a last-minute party, or just make any old Tuesday a little sweeter.

You’ll find all of her tips and tricks for being ready to make a dessert quickly on a moment’s notice, plus recipes for everything from cakes and cookies and cobbler and crisps to bars and ice cream and no-bake treats. Plus so much more.

What if I am gluten free? Should I still buy this book?

In Mary’s previous books and for many of the recipes on her website, she offers gluten free swaps. She did not do that in this book. But there are still a number of naturally gluten free recipes, like these gluten free Monster Cookie Bars, as well as flourless Mexican Chocolate Lava Cakes. There is an entire chapter of ice cream, puddings, and sauces that don’t contain gluten ingredients. And most of the no-bake desserts can be made gluten free by using a few simple swaps, like gluten free chocolate sandwich cookies or pretzels.

And honestly, I’d compare some of these recipes to those on her site where she gives the gluten free flour substitution. You might find a similar recipe, and with some experimentation, you might come up with a brand new gluten free dessert to love.

A stack of two No Flour Monster Cookie Bars on a small white plate

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More recipes from amazing cookbooks:

Here are more Monster Cookie-inspired recipes:

Gluten Free Monster Cookie Bars Recipe

Bar cookies are the ultimate make-ahead dessert. And these Monster Bars are definitely one of the best. You can mix them up in one bowl in just minutes and bake them in a single pan with no fuss. And they are chock full of peanut butter, oats, chocolate chips, and M&M’s. Plus, these no flour cookie bars are naturally gluten free. Guaranteed to be a family favorite!

I hope you’ll leave a comment and give it a FIVE STAR rating or share a review on Pinterest or photo on Instagram!
Tag me @cupcakekalechip and use #cupcakesandkalechips!

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A stack of two No Flour Monster Cookie Bars on a small white plate
5 from 1 vote

Monster Cookie Bars

A fully-loaded bar cookie you can make in one bowl in no time. Crisp on the outside, chewy on the inside, and filled with peanut butter, oats, chocolate chips, and M&M's.
Prep: 15 mins
Cook: 16 mins
Servings: 9 bars

Ingredients

  • 3 Tablespoons butter, softened
  • 3/4 cup light brown sugar
  • 1/3 cup white sugar
  • 1 egg
  • 1 egg yolk
  • 1 teaspoon vanilla extract
  • 1 Tablespoon maple syrup
  • 1/2 teaspoon baking soda
  • 2/3 cup crunchy peanut butter
  • 2 cups old-fashioned rolled oats, certified gluten free if needed
  • 1/3-1/2 cup semi-sweet chocolate chips
  • 1/4-1/2 cup M&M's candies for topping

Instructions

  • Preheat the oven to 350°F. Line an 8-inch square pan with parchment paper or grease well with butter.
  • Combine the butter, brown sugar, and white sugar in a large bowl and beat to combine. Add the egg, egg yolk, vanilla, syrup, and baking soda. Stir in the peanut butter. Add the oats and stir until well combined. Mix in the chocolate chips.
  • Press the dough into the bottom of the prepared pan. Top with the M&M's and lightly press them into the dough. Bake 16 to 17 minutes, or until the bars are lightly browned and just past looking wet on top. They will not be firm, but they will set up as they cool. Let it cool completely before slicing. Store in an airtight container.

Notes

  • While it says you can butter your pan well, lining the pan with parchment paper is definitely recommended. Let the parchment overhang the edges by at least an inch, then use the edges to pull the entire thing out at once. This makes it easier to slice the cooled bars on a cutting board.
  • The recipe calls for salted butter. If you only have unsalted butter, just add a pinch of salt.
  • When measuring peanut butter, grease your measuring cup with butter or cooking spray so it slides out easily.
  • Let them cool for at least 15 minutes. There will be some carryover cooking, they will be easier to cut, and you definitely want to store fully cooled bars.
  • Baking for someone avoiding gluten? These are perfect because they are flourless, but if you are dealing with celiac or an allergy, make sure your oats are certified gluten free.
  • Once you have mastered the basic version, try switching it up with different nut butters and candy mix-ins.
Nutrition Facts
Monster Cookie Bars
Amount Per Serving (1 bar)
Calories 449.01 Calories from Fat 199
% Daily Value*
Fat 22.11g34%
Saturated Fat 8.82g44%
Cholesterol 52.25mg17%
Sodium 205.13mg9%
Potassium 282.02mg8%
Carbohydrates 56.12g19%
Fiber 4.08g16%
Sugar 39.44g44%
Protein 9.32g19%
Vitamin A 197.74IU4%
Calcium 61.26mg6%
Iron 2.17mg12%
* Percent Daily Values are based on a 2000 calorie diet.

Enjoy!

4 Comments
  1. Mary

    5 stars
    I am so happy that you’re enjoying the cookbooks! These bars look fantastic and now I want to make them again. We love them too!

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