As much as my family loves it when I make brownies or cookies, they have a soft spot for dessert bars. Two of our firm favorites are peanut butter cookie bars and chocolate chip cookie bars, and recently, I’ve added monster cookie bars into my dessert baking rotation. These bars are inspired by my oatmeal chocolate chip bars and also my OG monster cookies. They get their “monster” name from the plethora of ingredients that go into the cookie dough, from creamy almond butter to M&Ms and warm cinnamon. The results speak for themselves: chewy, soft, chocolaty dessert bars filled with rich flavor and hearty oats.
Recipe Highlights
Flourless. I didn’t use any gluten-derived ingredients, so everyone can enjoy these decadent bars. Oh, and they’re easy to make vegan, too! Incredible flavor and texture. The exterior gets a subtle crunch from the brown sugar, while the middle is filled with gooey chocolate candy. Trust me, these bars will be gone before you know it. Easy to customize. You can change up the candy, add chopped nuts, or use different nut or seed butters. Easy to make. All you have to do is mix the dry and wet ingredients, fold in the M&M candies, then let them bake. It’s that simple, and the total prep time is just 5 minutes.
What we love about these bars is how deceptively healthy they are! The almond butter adds a little protein, while the quick oats and oat flour pack a ton of fiber, making them a satisfying and flavorful treat I can feel good about sharing with my family and friends.
Ingredients needed
In addition to tasting great, these bars come together with simple baking ingredients. Here’s everything you’ll need:
Large eggs. Room temperature eggs are best. Light brown sugar. I used light brown sugar for a minimal amount of molasses flavor, but you could use dark brown sugar for more molasses. Almond butter. For a thick, creamy texture and rich nutty flavor. Not a fan of almond butter? Swap it for creamy peanut butter to make peanut butter oatmeal cookie bars! Butter. I used unsalted butter since we’re adding salt to the cookie dough. Vanilla extract. A must for any good baking recipe! Quick oats. AKA instant oats, used to add a chewy texture. Rolled oats (also known as old-fashioned oats) could also work, too. Oat flour. I like to use oat flour when it comes to baking because it absorbs moisture well and adds fiber and a chewy texture. Baking powder. Our leavening agent to help the bars rise. Make sure to use baking powder and NOT baking soda, as baking soda requires an acidic ingredient to work. Salt. Just a dash to elevate the rest of the ingredients. Cinnamon. I like how the cinnamon complements the rest of the ingredients, but you could leave this out if preferred. M&Ms. For the classic monster cookie look, of course! Use regular M&Ms, vegan, or sugar-free candy buttons if you prefer.
Find the printable recipe with measurements below.
How to make monster cookie bars
Step 1- Prep work. Preheat the oven to 350F/180C and line an 8×8-inch baking pan with parchment paper. Step 2- Combine wet ingredients. In a large mixing bowl or the bowl of a standing mixer, cream the melted butter and all remaining wet ingredients. Stir to fully combine. Step 3- Add dry ingredients. Add dry ingredients to the bowl and mix until a batter forms. Fold in the M&Ms and mix to combine. Step 4- Form bars. Transfer the cookie bar dough to the prepared pan and spread it into an even layer. Add more M&Ms if desired. Step 5- Bake. Bake the bars for 18-25 minutes, depending on how gooey you prefer the bars. Once they’re done cooking, let them cool completely before slicing.
Recipe tips and variations
Make them vegan. When I’m making these bars for my vegan friends, I’ll swap the eggs for equal parts flax eggs and use plant-based butter and dairy-free candy buttons. Make them nut-free. If someone you know has a nut allergy, swap the almond butter for sunflower seed butter or tahini. Switch up the candy buttons. Use whatever flavor of M&Ms you have on hand, or use a combination of candy buttons and Reese’s pieces. If I’m making these bars for Christmas, I like to use red and green M&Ms. Add chocolate chips. Just in case there isn’t already enough chocolate in this recipe, feel free to fold in white chocolate chips, dark chocolate chips, milk chocolate chips, or even butterscotch chips. Add extra mix-ins. I sometimes like to add dried fruit, chopped nuts, or pretzel pieces, depending on what I have on hand. Top with flaky sea salt. For a little sweet and savory flavor, I like to sprinkle the bars with sea salt when they’re fresh out of the oven.
Storage instructions
To store: Store leftover cookie bars in an airtight container and keep them at room temperature for 2-3 days. Store the bars in the refrigerator for up to 1 week to keep them fresher for longer. To freeze: Wrap the sliced bars in plastic wrap or parchment paper, then freeze them in a freezer-safe container for up to 3 months. Let the frozen bars thaw overnight before enjoying.
Frequently asked questions
More dessert bar recipes to try
Zucchini bars– Healthy bars full of decadent chocolaty flavor. Caramel slice– Trust me, you won’t be able to stop with one!
Recipe originally published July 2019 but updated to include new information and an updated recipe for your benefit.
