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Crisp on the outside and chewy on the inside, these Monster Cookie Bars are fully-loaded with peanut butter, oats, chocolate chips, and M&M candies. But they have no flour, making them a naturally gluten free flourless dessert recipe. Even better, you can make them with less than 15 minutes of work and in only one bowl!
Love these? Then you have to try Gluten Free Brookies!
Best Monster Cookie Bar Recipe – One Bowl!
Unless I am baking for the blog, finding the time to make a special treat for the family 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.
Then I discovered these Monster Bars, and I have to be honest, it’s a little dangerous. Well, dangerously delicious. With the gooey middle, peanut butter overload, and double dose of chocolate, these bars are chock full of something to make everyone happy.
Even those who are gluten free! Monster Cookies are traditionally a flourless cookie, and this recipe is as well.
Monster Cookie Bars come together in about 15 minutes using basic ingredients you probably already have in your pantry. You only have to dirty one bowl, and there is no scooping or shaping. Just spread the dough in a pan, and they bake up fast.
Whether you want a quick and easy dessert to treat the family, are looking for something to make quickly to share with friends, are trying to bake something simple for someone avoiding gluten, or need a recipe for leftover Halloween candy, these no-flour cookie bars are guaranteed to be a family favorite!
Here’s a little information about what you’ll need to make these Monster Cookie Bars. For the full quantities and detailed directions, keep scrolling down to the recipe card. Or continue reading for more information about the recipe with lots of tips and tricks.
- Salted butter: Be sure it is softened to room temperature. If you only have unsalted butter, just add a pinch of salt to the recipe.
- Light brown sugar: Make sure it is lightly packed.
- White sugar: Yes, the blend of sugars makes them perfect.
- Egg plus egg yolk: Using both adds to the chewy texture.
- Vanilla extract: I recommend pure instead of imitation for the best flavor.
- Maple syrup: Use the real stuff, not pancake syrup, because that pure maple flavor complements the peanut butter.
- Baking soda: For that perfect rise, NOT baking powder.
- Crunchy peanut butter: You can use creamy, but the chunky adds a nice texture.
- Old-fashioned rolled oats: Not quick or instant oats. If these are being served to someone with celiac disease or a severe allergy or sensitivity, be sure to use certified gluten free rolled oats.
- Semi-sweet chocolate chips: Milk chocolate chips can also be substituted if you prefer.
- M&M’s candies: This recipe calls for the classic kind, but you can use holiday ones or other flavors.
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.
How to Make No Flour Monster Cookie Bars
Before you get started, preheat your oven to 350°F and line your pan with parchment paper. The Monster Cookie Bar dough comes together so quickly that you want to make sure the oven is hot and ready to go.
Cream the mixture. With a hand mixer, beat the butter and sugars in a large bowl. Blend in the egg, egg yolk, vanilla, maple syrup, and baking soda, followed by the peanut butter.
Add the dry ingredients. Use a spatula to mix in the oats and the chocolate chips.
Bake the bars. Press the dough into the pan. Sprinkle the M&M’s on top and lightly press into the dough. Bake for 16 to 17 minutes, or until lightly browned, but not completely firm.
Cool and slice. Let the bars cool completely in the pan on a rack before slicing. They will continue to firm up as they come to room temperature. Store on the counter in an airtight container for up to several days.
Can You Freeze Monster Cookie Bars?
Yes, bar cookies are one of the ultimate make-ahead desserts. While they will stay good for several days at room temperature if you keep them tightly wrapped, they also freeze well.
Let them cool completely and cut them into bars. You can then place the bars in an airtight container. For extra protection from freezer burn if you will be keeping them frozen for more than a month, I recommend placing the container in a freezer storage bag or wrapping it in plastic wrap. You can also wrap the bars in plastic and then place them into a freezer storage bag.
You can keep them frozen for up to two months.
Tips for Success
These monster bars are super easy to make. But a few tips will ensure they turn out perfectly.
- Line the Pan: 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.
- Don’t Get Sticky: 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.
- Be Patient: 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.
- Gluten Free Note: 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 (learn more in my article Are Oats Gluten Free?).
- Get Creative: Once you have mastered the basic version, try switching it up with different nut butters and candy mix-ins.
The Weeknight Dessert Cookbook
This recipe is from 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 5 to 15 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.
Even though this is not a gluten free dessert cookbook, 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.
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!
Things You’ll Need
BAKING PAN: You’ll need an 8-inch square baking pan for these bars.
PARCHMENT PAPER: Lining the pan makes it easier to remove the bars
HAND MIXER: You can mix these bars by hand, but a hand mixer will make it easier to blend the butter and sugars together.
SPATULAS: I love this set of silicone spatulas and use several of them on a daily basis. The larger ones are great for mixing the oats and chocolate chips, and pressing the dough into the pan.
More Monster Cookie recipes
- Monster Cookie Dough Dip
- Toffee White Chocolate Chip Almond Butter Monster Cookies
- Trail Mix Monster Cookies
- Snickers Monster Cookie Pie
Monster Cookie Bars
- 3 Tablespoons salted 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
- 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.
- 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.
What else can you use for topping; chocolate chips?
Sure! Or peanut butter chips, or another chopped candy!
Would steel cut oats work for this recipe?
I do not think so as they take a long time to cook, so would still be hard.
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!
I can’t wait to make them again myself!