The Ultimate Guide to Easy, Chewy Monster Cookie Bars (No-Chill Recipe!)

Prepare to fall in love with these incredibly soft and irresistibly chewy monster cookie bars! Each bite is a delightful explosion of flavors, generously loaded with creamy peanut butter, wholesome oats, melty chocolate chips, and vibrant M&M’s. What makes this recipe truly outstanding is its simplicity: it uses an easy, no-chill cookie dough that transitions directly from your mixing bowl to the oven, meaning less waiting and more enjoyment!

This streamlined recipe effortlessly transforms classic monster cookies into convenient and shareable bars. The cookie dough itself boasts a rich peanut butter base, perfectly complemented by a delightful scattering of hearty oats, luscious chocolate chips, and colorful M&M’s in every single square. These bars capture all the beloved flavors and textures of traditional monster cookies but in an even easier-to-make format that’s perfect for any occasion.

One of the biggest advantages of these monster cookie bars is their incredible softness and chewiness, a texture that holds up beautifully. Since the dough is simply pressed into a pan rather than portioned into individual cookies, there’s absolutely no chilling required. This cuts down significantly on prep time, making them a fantastic choice when you need a delicious treat in a hurry. Furthermore, the entire process utilizes just one mixing bowl, leading to minimal cleanup and a hassle-free baking experience. It’s truly a recipe designed for maximum flavor with minimum effort!

These crowd-pleasing monster cookie bars are an ideal addition to virtually any event. Whether you’re planning for festive holiday parties, participating in a lively cookie exchange, or simply looking for a delightful homemade dessert to share with family and friends, they are sure to be a hit. Their vibrant appearance and irresistible taste make them stand out. For an extra touch of seasonal flair, you can easily customize this recipe by using M&M’s in colors that match any upcoming holiday or special occasion, adding a personal and festive touch to your baking.

Essential Ingredient Notes for Perfect Monster Cookie Bars

Understanding the role of each ingredient is key to achieving the best possible texture and flavor in your monster cookie bars. Here’s a deeper dive into what you’ll need and why:

• Peanut Butter: For these bars, it’s crucial to use a creamy, no-stir peanut butter. Brands like Jif or Skippy are perfect because their consistent texture helps bind the dough effectively. Natural peanut butter, which often separates and has a thinner consistency, can make the bars greasy and alter the overall structure. The added oils in natural varieties tend to interfere with the delicate balance of fats and moisture needed for a perfectly chewy bar.
• Oats: I’ve successfully tested this recipe with both old-fashioned rolled oats and quick oats. While both work, I highly recommend using old-fashioned rolled oats. They provide a more substantial, chewier texture and a delightful rustic bite, enhancing the overall experience of the monster cookie bar. Quick oats will yield a softer, less defined texture, which is still delicious but less traditional for monster cookies.
• Light Brown Sugar: This isn’t just for sweetness; light brown sugar plays a vital role in keeping your cookie bars incredibly moist and chewy. Its molasses content adds depth of flavor, contributing to the characteristic richness of monster cookies. If you find yourself without brown sugar, don’t worry! You can easily make your own brown sugar by combining granulated sugar with a touch of molasses.
• Eggs: This recipe calls for one whole large egg plus an additional egg yolk. The extra egg yolk is a secret weapon in many cookie recipes, as it adds a significant richness and contributes to a wonderfully soft and tender crumb. The fat in the yolk helps create a more decadent texture. Don’t let the extra egg white go to waste! You can save it for other delicious recipes such as candied almonds, candied pecans, or simply add it to your morning egg scramble for an extra protein boost.
• M&M’s: While I used classic M&M’s in this recipe, the beauty of these bars is their versatility. Feel free to use any color or variety of M&M’s you prefer. Seasonal M&M’s are fantastic for holiday baking, allowing you to customize the bars for events like Christmas (red and green), Valentine’s Day (red, pink, white), or Halloween (orange, black, purple). Their candy shell adds a delightful crunch and burst of color.
• Chocolate Chips: To balance the sweetness from the M&M’s and brown sugar, I opted for semi-sweet chocolate chips. They provide a rich chocolatey flavor without making the bars overly sweet. However, feel free to experiment with other types like milk chocolate for a sweeter profile, dark chocolate for a more intense cocoa hit, or even white chocolate chips for a different flavor dynamic.
• All-Purpose Flour: The foundation of our cookie bars, all-purpose flour provides structure. Make sure to measure it correctly by spooning it into the measuring cup and leveling it off, rather than scooping directly from the bag, which can lead to too much flour and dry bars.
• Baking Soda: This leavening agent reacts with the brown sugar (which is acidic) to create carbon dioxide, resulting in a slightly lifted, chewy texture. It’s essential for the signature ‘soft bake’ of these bars.
• Salt: A pinch of salt is vital for balancing the sweetness and enhancing all the other flavors, especially the peanut butter and chocolate. Don’t skip it!

How To Make Irresistible Monster Cookie Bars: Step-by-Step Guide

Creating these delightful monster cookie bars is a straightforward process, perfect for bakers of all skill levels. Follow these simple steps to achieve perfectly soft, chewy, and loaded bars every time.

1. Prepare Your Pan and Oven: First, preheat your oven to 350°F (177°C). This ensures your oven is at the correct temperature when the dough is ready, promoting even baking. Next, line a 9×13-inch baking dish with parchment paper or foil, making sure to leave some overhang on the sides. This overhang acts as “handles” later, allowing you to easily lift the cooled bars out of the pan. Lightly spray the lined pan with non-stick cooking spray for extra insurance against sticking, then set it aside.
2. Combine the Wet Ingredients: In a large mixing bowl – remember, this is a one-bowl wonder! – whisk together the melted unsalted butter and creamy peanut butter until they are thoroughly combined and smooth. Then, add the packed light brown sugar to this mixture and whisk until it’s well incorporated, creating a creamy and sweet base.
3. To the peanut butter mixture, whisk in the large egg, the extra egg yolk (for that added richness and tenderness!), and the pure vanilla extract. Continue whisking just until everything is combined and the mixture is smooth, but be careful not to overmix at this stage.

3. Incorporate the Dry Ingredients: To the same mixing bowl (hooray for less cleanup!), add the all-purpose flour, old-fashioned rolled oats, baking soda, and salt. Stir these ingredients into the wet mixture using a sturdy spoon or a rubber spatula until just combined. Be careful not to overmix the dough once the flour is added, as this can lead to tougher bars. Stop mixing as soon as no streaks of dry flour remain.
4. Fold in the Delicious Mix-ins: This is where the “monster” truly comes to life! Using a rubber spatula, gently fold in the M&M’s and semi-sweet chocolate chips. Ensure they are evenly distributed throughout the dough so that every single bar gets a generous share of these colorful and chocolatey additions.

5. Transfer and Press into Baking Dish: Scoop the entire batch of cookie dough into your prepared 9×13-inch baking dish. Using the back of a spoon or your hands (lightly greased if it’s too sticky), press the cookie dough down firmly and evenly into one uniform layer. Ensure the dough reaches all corners and has a smooth top. For an extra aesthetic touch, you can press a few more M&M’s and chocolate chips onto the surface before baking.
6. Bake to Perfection: Place the baking dish in your preheated oven and bake for approximately 23 to 28 minutes. You’ll know the bars are done when the top looks set (no longer shiny or wet in the center) and has a light golden-brown hue around the edges. A toothpick inserted into the center should come out mostly clean with just a few moist crumbs attached, indicating a perfectly baked, chewy interior. It’s better to slightly underbake than overbake for maximum chewiness!
7. Cool Completely Before Slicing: This is a crucial step for achieving neatly sliced bars. When the bars first come out of the oven, they will be very soft and fragile. Resist the urge to cut into them immediately! Transfer the pan to a wire rack and allow the bars to cool completely in the pan. This cooling process allows them to set and firm up properly, making them much easier to remove and slice without crumbling. Once fully cooled, use the parchment paper overhang to lift the entire slab of cookie bars out of the pan, then slice into your desired serving sizes. Enjoy your delicious homemade monster cookie bars!

Exciting Recipe Variations for Your Monster Cookie Bars

While these monster cookie bars are fantastic in their classic form, they are also incredibly adaptable. Don’t hesitate to get creative and personalize them to your taste or for specific occasions! Here are some ideas to inspire your next batch:

• Peanut Butter Substitutions: If you have dietary restrictions or simply want to try a different flavor profile, the peanut butter can be replaced with another creamy, no-stir nut or seed butter. Almond butter, cashew butter, or even sunflower seed butter (for nut-free options) can work well, though they may slightly alter the flavor and texture. Ensure the substitute is also a “no-stir” variety for best results.
• M&M’s Galore: The M&M’s are a signature element, and their versatility is endless! As mentioned, use seasonal M&M’s to perfectly match any holiday – think red and green for Christmas, pastel colors for Easter, red and blue for the 4th of July, or autumnal shades for Thanksgiving. Beyond colors, you can also experiment with different M&M varieties like peanut M&M’s for extra crunch, pretzel M&M’s for a sweet and salty twist, or even mini M&M’s for a more subtle distribution of candy. You can also replace M&M’s entirely with chopped mini peanut butter cups, Reese’s Pieces, or other small candies.
• Chocolate Chip Choices: I recommend semi-sweet chocolate chips for a balanced flavor, but your choice of chocolate can significantly change the bar’s character. Milk chocolate chips will make the bars sweeter and creamier, while dark chocolate chips will add a deeper, more sophisticated cocoa note. For a different twist, consider white chocolate chips, butterscotch chips, or if you’re a true peanut butter fanatic, peanut butter chips would be an absolutely delicious addition, intensifying that nutty flavor.
• Additional Mix-ins: Take your monster cookie bars to the next level with even more exciting additions!
  • Nuts: Add chopped peanuts, pecans, or walnuts for extra crunch and nutty flavor. Toasting them lightly beforehand can enhance their aroma.
  • Pretzels: Crushed pretzels can introduce a wonderful salty-sweet contrast and a satisfying crunch.
  • Coconut: Shredded coconut (sweetened or unsweetened) adds a tropical hint and chewy texture.
  • Toffee Bits: For a buttery, caramel-like flavor, stir in some toffee bits.
  • Dried Fruits: While less traditional for monster cookies, dried cranberries or raisins could add a unique chewiness and tartness.

Monster Cookie Bars

Prep Time: 20 minutes mins

Cook Time: 25 minutes mins

Total Time: 45 minutes mins

These soft and chewy monster cookie bars are the ultimate easy dessert, packed with creamy peanut butter, wholesome oats, rich chocolate chips, and colorful M&M’s. This is a truly simple, no-chill cookie dough recipe that goes straight from your mixing bowl to the oven, making it perfect for quick baking projects or when you need a crowd-pleasing treat without the fuss. Enjoy all the beloved flavors of monster cookies in a convenient, shareable bar format!

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Ingredients

Yields: 24 bars

• ▢ ¾ cup unsalted butter melted and cooled for 10 minutes (170 grams; 1.5 sticks)
• ▢ ¾ cup creamy peanut butter (190 grams) avoid natural peanut butter
• ▢ 1 ½ cups packed light brown sugar (300 grams)
• ▢ 1 large egg at room temperature
• ▢ 1 large egg yolk at room temperature
• ▢ 1 teaspoon pure vanilla extract
• ▢ 1 ½ cups all-purpose flour spooned & leveled (190 grams)
• ▢ 1 ½ cups old-fashioned rolled oats (150 grams)
• ▢ ½ teaspoon baking soda
• ▢ ¼ teaspoon salt
• ▢ 1 cup M&M’s (215 grams)
• ▢ ¾ cup semi-sweet chocolate chips (135 grams)

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Instructions

 

• Preheat the oven to 350°F (177°C).
• Line a 9×13-inch pan with foil or parchment paper, leaving some overhang on all sides for easy removal. Spray with nonstick cooking spray and set aside.
• In a large mixing bowl, whisk together the melted butter and creamy peanut butter until well combined and smooth. Then, whisk in the packed light brown sugar until thoroughly incorporated.
• Add the large egg, egg yolk, and vanilla extract to the mixture. Whisk until just combined, ensuring no streaks of egg remain.
• To the same bowl, add the all-purpose flour, old-fashioned rolled oats, baking soda, and salt. Stir with a rubber spatula or spoon until the dry ingredients are just incorporated and no flour pockets are visible. Be careful not to overmix.
• Gently fold in the M&M’s and semi-sweet chocolate chips using a rubber spatula until they are evenly distributed throughout the dough.
• Scoop the cookie dough into the prepared 9×13-inch pan. Using the back of a spoon or your hands, press the dough down firmly and evenly into one smooth, uniform layer. For a more appealing top, you can press a few additional M&M’s and chocolate chips onto the surface before baking.
• Bake for 23 to 28 minutes, or until the tops of the bars are set and very lightly golden brown around the edges. A toothpick inserted into the center should come out mostly clean with just a few moist crumbs attached. Avoid overbaking for a chewier texture.
• Remove the pan from the oven and transfer it to a wire rack. Allow the bars to cool completely in the pan before attempting to remove or slice them. This is crucial for them to set properly.
• Once fully cooled, use the parchment paper overhang to lift the entire slab of cookie bars out of the pan. Place them on a cutting board and slice into your desired bar sizes. Serve and enjoy these delicious, chewy monster cookie bars!

Notes

Storage Instructions: To maintain their freshness and chewiness, store your monster cookie bars in an airtight container at room temperature for up to one week.

Freezing Instructions: These bars freeze exceptionally well, making them perfect for meal prep or future cravings. You can freeze them for 2 to 3 months. For best results, wrap individual bars tightly in plastic wrap, then place them in an airtight freezer-safe container or bag. Thaw to room temperature before serving for optimal texture and flavor.

Cuisine: American

Course: Dessert, Snack

Author: Danielle Rye

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