If you’re craving a sweet, chewy, and colorful treat but don’t want to commit to a giant batch, these Small-batch Monster Cookie Bars are exactly what you need. Loaded with peanut butter, oats, M&Ms, and chocolate chips, they’re a delightful twist on the classic monster cookie—perfectly portioned for a quick bake and satisfying a sweet tooth without leftovers. These bars bring together the best of chewy and crunchy textures with bursts of chocolate and candy-coated goodness in every bite.
Why I Love This Recipe
Small-batch Monster Cookie Bars are a game changer for several reasons. First, the small batch size means you can whip up a fresh, warm treat in no time without worrying about excess cookies lingering around for days. The combination of salty butter and creamy peanut butter provides a rich base while the oats add a hearty texture and a touch of wholesomeness. The M&Ms and chocolate chips not only bring vibrant pops of color but also melt into gooey pockets of chocolate that make these bars irresistible. Plus, they’re incredibly easy to customize with your favorite mix-ins!
Your Shopping Guide
- Salted Butter (3 tablespoons / 42g, softened): Using salted butter adds a subtle savory balance to the sweetness. Make sure it’s softened for easy mixing.
- Peanut Butter (1/2 cup / 132g): Creamy or chunky both work wonderfully here. Choose natural or store-bought peanut butter without added sugar or hydrogenated oils.
- Granulated Sugar (1/3 cup / 67g): Regular white sugar helps with texture and sweetness.
- Brown Sugar (1/3 cup / 67g): Adds moisture and a caramel-like depth of flavor.
- Egg (1 large): Acts as a binder to hold the bars together.
- Vanilla Extract (1/2 teaspoon): Enhances all the flavors.
- Quick/Instant Oats (1 1/2 cups / 130g): Provides chewiness and structure. Rolled oats can be used but the texture will be slightly different.
- Baking Soda (1/2 teaspoon): Helps with leavening and the perfect rise.
- M&Ms (1/2 cup / 85g) plus more for topping: Adds color, crunch, and chocolate. Feel free to use peanut-free or allergy-friendly versions if needed.
- Chocolate Chips (1/3 cup / 56g): Semi-sweet or milk chocolate chips work well for melty pockets of richness.
Prep & Cook Tools
- Mixing Bowls: At least one medium bowl for combining ingredients.
- Hand Mixer or Stand Mixer: For creaming the butter and sugars smoothly.
- Spatula: To fold in the oats, chocolate chips, and M&Ms without overmixing.
- 8×8-inch Baking Pan: Perfect size for this small batch and easy to cut into bars.
- Parchment Paper: To line the pan for easy removal and cleanup.
- Measuring Cups and Spoons: For accurate ingredient portions.
- Cooling Rack: To cool the bars completely before slicing.
Cooking Small-batch Monster Cookie Bars: The Process
Step 1: Preheat and Prep
Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving some overhang on the sides to help lift the bars out easily once baked.
Step 2: Cream Butter and Sugars
In a medium bowl, combine the softened salted butter, peanut butter, granulated sugar, and brown sugar. Using a hand mixer or stand mixer, beat until the mixture is light and fluffy – about 2 to 3 minutes. This step is key for that perfect texture.
Step 3: Add Egg and Vanilla
Mix in the large egg and vanilla extract until fully incorporated. The batter will look smooth and creamy here.
Step 4: Combine Dry Ingredients
In a separate bowl, whisk together the quick oats and baking soda. Gradually add this to the wet mixture, folding gently with a spatula to combine everything without overmixing.
Step 5: Fold in the M&Ms and Chocolate Chips
Reserve a handful of M&Ms for topping. Fold the rest along with the chocolate chips into the batter evenly.
Step 6: Bake
Spread the batter evenly into the prepared baking pan. Sprinkle the reserved M&Ms on top for a colorful finishing touch. Bake for 20-25 minutes, or until the edges are golden and a toothpick inserted in the center comes out with a few moist crumbs.
Step 7: Cool and Slice
Allow the bars to cool completely in the pan on a wire rack. Use the parchment paper overhang to lift the bars out, then cut into squares or rectangles. Enjoy immediately or store for later!
Ingredient Swaps & Substitutions
- Peanut Butter: Substitute with almond butter, sunflower seed butter, or cashew butter for different nutty flavors or to accommodate allergies.
- M&Ms: Use any colorful candy-coated chocolates or skip them for a more chocolate chip-focused bar.
- Chocolate Chips: Swap with white chocolate, butterscotch chips, or chopped nuts for variety.
- Oats: Rolled oats can replace quick oats but expect a chewier texture.
- Butter: Use vegan margarine or coconut oil for a dairy-free version.
Recipe Notes & Chef’s Commentary
- Do not overbake! Bars will continue to set as they cool, so pull them from the oven when the center is just slightly soft.
- For extra chewiness, try adding a tablespoon of honey or maple syrup to the wet ingredients.
- Feel free to double the recipe and bake in a 9×13-inch pan for a larger batch.
- Using a mix of creamy and chunky peanut butter adds interesting texture contrast.
- Pressing some M&Ms on top before baking makes the bars look extra inviting and colorful.
Make Ahead Like a Pro
These Small-batch Monster Cookie Bars keep well in an airtight container at room temperature for up to 4 days. For longer storage, wrap tightly and freeze for up to 3 months. Thaw at room temperature before enjoying. You can also slice the bars before freezing and separate layers with parchment paper for easy grab-and-go snacking.
Popular Questions
Can I use natural peanut butter in this recipe?
Yes! Natural peanut butter works great, but because it tends to be oilier, you might notice a slightly softer texture. Make sure to stir it well before measuring.
What if I don’t have quick oats?
Rolled oats can be substituted, but the bars will be a bit chewier and less uniform. Instant oats may make the bars denser, so quick oats are ideal.
Can I make these bars nut-free?
Absolutely – swap the peanut butter for a seed butter like sunflower or soy nut butter, and use allergy-friendly candy in place of M&Ms.
How do I store leftover bars?
Store them in an airtight container at room temperature for up to 4 days, or freeze for longer shelf life. They’re delicious warmed slightly before serving.
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That’s a Wrap
If you want a colorful, chewy, and peanut buttery treat without the fuss of making a dozen cookies, these Small-batch Monster Cookie Bars are your new go-to. They’re quick to whip up, easy to customize, and satisfy every craving for chocolate and candy-coated crunch. Perfect as an afternoon snack, lunchbox treat, or simple dessert, these bars bring monster cookie magic to a perfectly sized batch. Give them a try and watch how fast they disappear!
Happy baking and snacking!
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Small-batch Monster Cookie Bars
Equipment
- Mixing Bowls
- Hand Mixer or Stand Mixer
- Spatula
- 8x8-inch baking pan
- Parchment Paper
- Measuring cups and spoons
- Cooling rack
Ingredients
- 3 tablespoons Salted Butter softened
- 1/2 cup Peanut Butter
- 1/3 cup Granulated Sugar
- 1/3 cup Brown Sugar
- 1 large Egg
- 1/2 teaspoon Vanilla Extract
- 1 1/2 cups Quick/Instant Oats
- 1/2 teaspoon Baking Soda
- 1/2 cup M&Ms plus more for topping
- 1/3 cup Chocolate Chips
Instructions
Cooking Small-batch Monster Cookie Bars: The Process
- Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving some overhang on the sides to help lift the bars out easily once baked.
- In a medium bowl, combine the softened salted butter, peanut butter, granulated sugar, and brown sugar. Using a hand mixer or stand mixer, beat until the mixture is light and fluffy – about 2 to 3 minutes.
- Mix in the large egg and vanilla extract until fully incorporated. The batter will look smooth and creamy here.
- In a separate bowl, whisk together the quick oats and baking soda. Gradually add this to the wet mixture, folding gently with a spatula to combine everything without overmixing.
- Reserve a handful of M&Ms for topping. Fold the rest along with the chocolate chips into the batter evenly.
- Spread the batter evenly into the prepared baking pan. Sprinkle the reserved M&Ms on top for a colorful finishing touch. Bake for 20-25 minutes, or until the edges are golden and a toothpick inserted in the center comes out with a few moist crumbs.
- Allow the bars to cool completely in the pan on a wire rack. Use the parchment paper overhang to lift the bars out, then cut into squares or rectangles. Enjoy immediately or store for later!
Notes
- Do not overbake! Bars will continue to set as they cool, so pull them from the oven when the center is just slightly soft.
- For extra chewiness, try adding a tablespoon of honey or maple syrup to the wet ingredients.
- Feel free to double the recipe and bake in a 9x13-inch pan for a larger batch.
