Chewy Monster Cookie Recipe

There are cookies, and then there are Monster Cookies. These aren’t just your average treat; they’re a full-blown comfort food experience. They combine the best parts of a peanut butter cookie, an oatmeal cookie, and a chocolate chip cookie into one gloriously chunky, soft, and chewy masterpiece.

After making this recipe more than nine times, tweaking and testing every variable, I can confidently say this is the ultimate monster cookie recipe. My goal was simple: to create a cookie that was thick, incredibly chewy, and stayed soft for days. This is that cookie. It’s the one my family requests for every gathering, and it’s about to become a staple in your home, too.

Why You’ll Love This Monster Cookie Recipe

This isn’t just another cookie recipe. This is the result of dedicated testing to achieve cookie perfection.

• Perfectly Chewy Texture: Thanks to a secret ingredient (corn starch!) and a specific method using cold butter, these cookies have an unbeatable soft and chewy bite that lasts.
• Loaded with Goodies: Every bite is packed with creamy peanut butter, wholesome oats, two kinds of chocolate chips, and colorful M&M’s. It’s a flavor and texture explosion!
• No Dough Chilling Required: While you can chill the dough for even thicker cookies, this recipe is designed to be bake-ready right away, getting you from craving to cookie in under 30 minutes.
• Tried, Tested, and True: As a seasoned recipe developer, I’ve poured my experience into this recipe. My 9+ test batches mean you get a flawless result on your very first try.

If you’re a true cookie fanatic like me, you know the joy of a perfect recipe. For other decadent treats, don’t miss my popular Stuffed Red Velvet Cookies or these amazing Peanut Butter Nutella Cookies.

What Are Monster Cookies?

Monster cookies are the “everything but the kitchen sink” of the cookie world. While variations exist, the classic formula is what makes them so special: a peanut butter and oatmeal-based dough loaded with chocolate chips and M&M’s. They get their name from their typically large, “monstrous” size and the monstrously delicious combination of ingredients.

They are the ultimate comfort food, reminding us of childhood bake sales and cozy afternoons. This recipe honors that tradition while elevating the texture to a truly bakery-quality level.

Ingredients You’ll Need

The magic of these cookies lies in using the right ingredients in the right way. Here’s what you’ll need and why each component is so important.

The Foundation

• Salted Butter: We use cold, cubed butter straight from the fridge. This is crucial for preventing the cookies from spreading too much, creating that desirable thick and chewy texture.
• Sugars: A combination of granulated sugar and brown sugar provides the perfect balance of sweetness, moisture, and chewiness. The molasses in the brown sugar is key for softness.
• Creamy Peanut Butter: This adds the signature nutty flavor and richness. Standard creamy peanut butter (like Jif or Skippy) works best; avoid natural peanut butters that can separate.
• Egg & Egg Yolk: One whole egg provides structure, while the extra egg yolk adds richness, fat, and chewiness, making the cookies extra decadent.
• Vanilla Extract: A non-negotiable for flavor depth.

The Dry Mix

• All-Purpose Flour: The structural backbone of the cookie.
• Corn Starch: My secret weapon for soft cookies! Corn starch makes the crumb incredibly tender and helps keep the cookies soft for days.
• Baking Soda: This is our leavening agent, giving the cookies just the right amount of lift.
• Salt: Balances all the sweetness and enhances the flavors of the peanut butter and chocolate.

The “Monster” Mix-Ins

• Quick Oats: These smaller oats blend beautifully into the dough, providing a chewy texture without being overly rustic.
• Chocolate Chips: I use a mix of milk chocolate chips and semi-sweet chocolate chips for a more complex chocolate flavor.
• M&M’s: The classic candy shell adds a delightful crunch and a pop of color. Mini M&M’s are fantastic for getting more candy in every bite!

Step-by-Step Instructions

Follow these simple steps for foolproof monster cookies every time.

Step 1: Prep and Combine Dry Ingredients

First, preheat your oven to a slightly higher temperature of 400°F (200°C). This helps the cookies set quickly on the outside, preventing them from spreading too much. Line a large baking sheet with parchment paper.

In a medium bowl, whisk together the all-purpose flour, corn starch, baking soda, and salt. Mixing these thoroughly now ensures they get evenly distributed in the dough later.

Step 2: Cream the Butter and Sugars

In the bowl of a stand mixer with the paddle attachment, beat the cold, cubed butter on medium-high for about a minute. It will break down and start to look creamy. Scrape the sides of the bowl and beat for another 30 seconds. This process is key to creating a thick cookie.

Add the brown and granulated sugars to the butter. Mix on medium speed until the mixture is light, fluffy, and fully combined.

Step 3: Add Wet Ingredients

Now, add the peanut butter, vanilla extract, whole egg, and egg yolk to the bowl. Mix on low speed just until combined. Overmixing at this stage can lead to dense cookies, so be gentle!

Step 4: Combine Wet and Dry

With the mixer on its absolute lowest speed, add the dry ingredient mixture in two or three additions. Mix only until the last streaks of flour have disappeared. You can even finish mixing by hand with a spatula to be extra safe against overmixing.

Step 5: Fold in the Goodies

Gently fold in the quick oats, both types of chocolate chips, and the M&M’s using a spatula or by running the mixer on its lowest setting for just a few seconds. The dough will be thick and chunky.

Step 6: Scoop and Bake

Using a large cookie scoop or your hands, form the dough into large balls. For truly monstrous, bakery-style cookies, I aim for about 165 grams of dough per cookie. Place them on your prepared baking sheet, leaving a few inches of space between each one.

For that irresistible, fresh-from-the-bakery look, gently press a few extra M&M’s and chocolate chips onto the tops of the dough balls before they go into the oven.

Bake on the middle rack for 10-12 minutes. The cookies are done when the edges are set and lightly golden, but the centers still look soft and slightly underbaked.

Step 7: The Crucial Cool Down

This might be the most important step! Let the cookies cool on the hot baking sheet for 10-15 minutes. This allows the centers to finish cooking through from the residual heat and set up properly. Do not skip this! After they’ve rested, transfer them to a wire rack to cool completely.

Sofie’s Expert Tips for Perfect Monster Cookies

1. Trust the Cold Butter: It feels wrong, but starting with cold butter is the secret to a thick, non-greasy cookie that doesn’t spread into a puddle.
2. Measure Flour Correctly: Spoon your flour into the measuring cup and level it off with a knife. Packing it in can add too much flour, resulting in dry, cakey cookies.
3. Don’t Skimp on the Mix-Ins: These are monster cookies! Be generous with the chocolate chips and M&M’s.
4. Slightly Underbake: The key to a soft, chewy center is to pull the cookies from the oven when they still look a little doughy in the middle. The residual heat on the pan will finish the job perfectly.
5. For Even Thicker Cookies: If you have the time, chilling the scooped cookie dough balls in the fridge for 30 minutes before baking will give you an even thicker, chewier result.

If you love unique cookie flavors, you should also check out my Pistachio NYC Cookies Recipe and these indulgent White Chocolate Stuffed Cookies.

How to Store Monster Cookies

These cookies have fantastic staying power thanks to the brown sugar and corn starch.

• At Room Temperature: Store the completely cooled cookies in an airtight container for up to 5 days. For extra softness, add a slice of bread to the container.
• Freezing Baked Cookies: Place the cookies in a single layer on a baking sheet and freeze until solid. Then, transfer them to a zip-top freezer bag. They’ll keep for up to 3 months. Thaw at room temperature.
• Freezing Dough: Scoop the dough balls onto a parchment-lined baking sheet and freeze until firm. Transfer the frozen dough balls to a freezer bag. You can bake them directly from frozen; just add 2-3 minutes to the baking time.

Frequently Asked Questions (FAQ)

What makes a monster cookie a monster cookie?
A classic monster cookie is defined by its core ingredients: peanut butter, oats, chocolate chips, and M&M’s. It’s a ‘kitchen sink’ style cookie that combines the best parts of a peanut butter cookie, an oatmeal cookie, and a chocolate chip cookie into one delicious treat.

Can I use old-fashioned oats instead of quick oats?
Yes, you can substitute old-fashioned (rolled) oats for quick oats. Using old-fashioned oats will result in a slightly chewier, more textured cookie. Quick oats, being smaller and thinner, tend to blend more seamlessly into the dough for a softer bite. Both are delicious, so it’s a matter of personal preference!

Why are my monster cookies flat?
Flat cookies are often caused by butter that is too soft or melted. This recipe specifically calls for cold, cubed butter to prevent spreading. Another culprit could be overmixing the dough after adding the flour, which develops too much gluten. For extra insurance against spreading, you can chill the cookie dough balls for 30 minutes before baking.

I can’t wait for you to try this perfected Monster Cookie recipe. It’s a true labor of love that I’m so proud to share. If you make them, please leave a comment and a rating below—I love hearing from you! And if you’re looking for an Easter treat, my Creme Egg Stuffed Cookies are always a huge hit!

Enjoy your new favorite cookie

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