If you’re looking for a sweet treat that’s easy to make and satisfies your craving for something deliciously indulgent, you’re in the right place. These Small-batch Monster Cookie Bars combine the best elements of cookies and bars, packed with oats, peanut butter, M&Ms, and chocolate chips. Perfect for a quick dessert or a midday snack, these bars are a crowd-pleaser that can be whipped up in just a handful of steps.
The Upside of Small-batch Monster Cookie Bars

The beauty of Small-batch Monster Cookie Bars lies in their simplicity and portion control. By making a smaller batch, you can indulge without the guilt of having a whole tray of cookies calling your name. These bars are perfect for satisfying a sweet tooth while avoiding the temptation of leftovers. Plus, they’re quick to prepare, making them an ideal choice for last-minute gatherings or a cozy night in.
Gather These Ingredients
Before you dive into the baking process, let’s gather the necessary ingredients. You’ll need:
- 3 tablespoons (42g) salted butter, softened
- 1/2 cup (132g) peanut butter, creamy or chunky
- 1/3 cup (67g) granulated sugar
- 1/3 cup (67g) brown sugar
- 1 large egg
- 1/2 teaspoon vanilla extract
- 1 1/2 cups (130g) quick/instant oats
- 1/2 teaspoon baking soda
- 1/2 cup (85g) M&Ms, plus more for topping
- 1/3 cup (56g) chocolate chips
Equipment & Tools
To make your baking experience smooth, gather the following tools:
- Mixing bowls – For combining your ingredients.
- Spatula – Perfect for mixing and spreading the batter.
- 8×8-inch baking pan – Ideal for the small batch size.
- Parchment paper – For easy removal of the bars from the pan.
- Oven – To bake your delicious bars.
Small-batch Monster Cookie Bars Made Stepwise

Now that you have everything ready, let’s get into the steps for making these delightful Small-batch Monster Cookie Bars.
Step 1: Preheat Your Oven
Preheat your oven to 350°F (175°C). This ensures your bars bake evenly and perfectly.
Step 2: Prepare Your Baking Pan
Line an 8×8-inch baking pan with parchment paper, allowing some overhang for easy removal later. This step is key in ensuring your bars don’t stick to the pan.
Step 3: Mix the Wet Ingredients
In a mixing bowl, combine the softened butter and peanut butter. Use a spatula or electric mixer to blend them until smooth. Add in the granulated sugar, brown sugar, egg, and vanilla extract. Mix until everything is well incorporated and creamy.
Step 4: Combine the Dry Ingredients
In another bowl, whisk together the quick oats and baking soda. Gradually add this dry mixture to the wet ingredients, stirring until just combined.
Step 5: Fold in the Goodies
Gently fold in the M&Ms and chocolate chips. Make sure they’re evenly distributed throughout the batter. Feel free to add a few extra M&Ms on top for a fun finishing touch!
Step 6: Spread and Bake
Pour the batter into your prepared baking pan, spreading it evenly with your spatula. Bake in the preheated oven for about 20-25 minutes, or until the edges are golden and a toothpick inserted in the center comes out clean.
Step 7: Cool and Cut
Once baked, remove the pan from the oven and let it cool completely in the pan. Once cooled, use the parchment paper overhang to lift the bars out and place them on a cutting board. Cut into squares and enjoy your Small-batch Monster Cookie Bars!
Spring to Winter: Ideas

These bars are versatile and can be adjusted to fit any season. Here are some ideas to consider:
- In spring, add some chopped dried fruits like apricots or cranberries for a fruity twist.
- During summer, mix in some shredded coconut for a tropical flavor.
- In the fall, incorporate pumpkin spice and some pumpkin puree for a festive treat, similar to Pumpkin Chocolate Chip Cookies.
- In winter, consider adding crushed peppermint candies to the mix for a refreshing, seasonal flair.
What Could Go Wrong
Baking is a science, and while these Small-batch Monster Cookie Bars are straightforward, a few pitfalls can occur:
- Overmixing the batter can lead to dense bars, so mix just until combined.
- Not cooling the bars completely before cutting can result in crumbly edges.
- Using incorrect measurements, especially for the flour or sugar, can affect the texture.
Store, Freeze & Reheat
To keep your Small-batch Monster Cookie Bars fresh, consider these storage tips:
- Store in an airtight container at room temperature for up to 5 days.
- For longer storage, freeze the bars in an airtight container or freezer bag for up to 3 months.
- To reheat, simply warm a bar in the microwave for 10-15 seconds to enjoy that fresh-baked taste again.
Frequently Asked Questions
Can I use natural peanut butter?
Yes, you can use natural peanut butter, but keep in mind that it may alter the texture slightly, making the bars denser. Ensure that the peanut butter is well-mixed before measuring.
What if I don’t have quick oats?
If you don’t have quick oats, you can use rolled oats, but you may need to adjust the baking time slightly as they take longer to cook.
Can I substitute the chocolate chips?
Absolutely! You can use white chocolate, butterscotch chips, or even chopped nuts for a different flavor profile.
Are these bars gluten-free?
To make them gluten-free, ensure that you use certified gluten-free oats and check that your baking soda is gluten-free.
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Next Steps
Now that you’ve got the inside scoop on making Small-batch Monster Cookie Bars, it’s time to roll up your sleeves and get baking! Whether you’re treating yourself or sharing with friends, these bars are sure to be a hit. Don’t forget to experiment with different mix-ins to create a version that’s uniquely yours. Happy baking!

Small-batch Monster Cookie Bars
Ingredients
- 3 tablespoons salted butter softened
- 1/2 cup peanut butter creamy or chunky
- 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
- Preheat your oven to 350°F (175°C) for even baking.
- Line an 8x8-inch baking pan with parchment paper, allowing some overhang for easy removal.
- In a mixing bowl, combine the softened butter and peanut butter. Blend until smooth, then add granulated sugar, brown sugar, egg, and vanilla extract. Mix until creamy.
- In another bowl, whisk together quick oats and baking soda. Gradually add to the wet mixture and stir until just combined.
- Fold in M&Ms and chocolate chips. Distribute them evenly in the batter.
- Pour the batter into the prepared pan, spreading evenly. Bake for 20-25 minutes or until edges are golden.
- Let cool completely in the pan, then lift out using parchment paper and cut into squares.
Equipment
- Mixing bowls
- Spatula
- 8x8-inch baking pan
- Parchment Paper
- Oven
Notes
- Store in an airtight container at room temperature for up to 5 days.
- Freeze in an airtight container for up to 3 months.
- Reheat in the microwave for 10-15 seconds for a fresh-baked taste.
