Monster Cookie Bars
These monster cookie bars deliver everything you love about monster cookies – chewy oats, peanut butter, mini M&Ms, and plenty of chocolate chips – all in an easy one-pan bar form. No scooping, no batches, no fuss: just press the thick dough into an 8×8 pan, bake for about 20 minutes, and you’ve got 16 thick, chewy squares ready to go. They’re a little wholesome (oats! peanut butter! eggs!) and a lot delicious, making them perfect for after-school snacks, lunchboxes, bake sales, or anytime you need a crowd-pleasing treat.
Hearty, sweet, and super-delicious.
These hearty bars have a lot packed into each sweet bite! They’re ideal for an after-school snack, lunchbox goodie, or a party treat.
I tested many versions of these bars as I was trying to initially make them without flour. But, they ended up a bit too crumbly. I also played with the amount and types of sugar and chocolate, landing on what I consider a pretty minimal amount for a dessert bar. They’re…
🥜 Packed with good stuff: Oats, peanut butter, and eggs make these bars hearty and genuinely satisfying.
😋 Chewy & chocolatey: Every bite is soft in the middle with M&Ms and chocolate chips throughout.
🛒 Pantry-friendly: You probably already have everything you need, no special ingredients required.
⏰ Ready in 30 minutes: Easy prep, minimal cleanup, and on the table fast.
❄️ Freezer-friendly: Make a batch, freeze the extras, and pull them out whenever you need a snack or treat.
🎉 Crowd-pleasing: Perfect for bake sales, lunchboxes, after-school snacks, or parties.
You’ll also want to try my s’mores bars, oreo rice krispie treats, and mini chocolate chip muffins.
Ingredient Notes
You’ll need some fresh ingredients and pantry staples to make these bars: butter, crunchy peanut butter (Jif or Skippy work great; avoid runny natural varieties), eggs, vanilla extract, old-fashioned oats, all-purpose flour, brown sugar, baking powder, salt, mini M&Ms (minis help the bars hold together better than regular-sized), and mini semi-sweet chocolate chips.
Emily’s Tips & Tricks
- Pro tip: Line your 8×8 pan with parchment paper with a little overhang on the sides. It acts as a sling and makes lifting the whole batch out effortless. If you skip the parchment, use a small spatula to scoop the bars out – it gets underneath the bottom so nothing sticks and you don’t leave the best bits behind.
- What I See: You might see a dessert bar, but I see more than that from a nutrition standpoint! I see energy (carbs), protein, fiber, and flavor – all important components in my nutrition opinion. Each square has 7 grams of protein and almost 3 grams of fiber – better nutrition stats than most granola bars! These will actually satisfy your hunger so I love them in the afternoon when I need something to get me to dinner.
- Variations: The mix-ins are really flexible here; most importantly, you want them in small pieces, but just about anything goes! Dried fruit and chopped almonds would also be delicious.
Monster Cookie Bars Recipe
- Prep Time: 10 minutes
- Cook Time: 20 minutes
- Total Time: 30 minutes
- Yield: 16 squares 1x
- Category: Dessert
- Method: Baking
Description
These monster cookie bars are soft, chewy, and packed with oats, peanut butter, chocolate chips, and M&Ms. A foolproof, crowd-pleasing treat!
Ingredients
- 1/2 cup butter (1 stick)
- 1 cup crunchy peanut butter (like Jiffy Naturals)
- 2 large eggs
- 2 tsp. vanilla extract
- 1 1/2 cups old-fashioned oats
- 1 cup all-purpose flour
- 1/2 cup packed brown sugar
- 1 tsp. baking powder
- pinch of salt
- 1/3 cup mini M&M’s
- 1/4 cup mini semi-sweet chocolate chips
Instructions
- Preheat oven to 375 degrees F.
- Prepare an 8×8-inch pan with cooking spray or line with parchment paper overhanging on the sides so you can lift the bars out.
- In a medium bowl, mix together oats, flour, brown sugar, baking powder, and salt.
- In a large bowl, melt butter. Add in peanut butter, eggs, and vanilla and whisk together until combined and smooth. Add dry ingredients, M&M’s, and chocolate chips to the wet ingredients and mix until a thick dough forms.
- Transfer the dough into the prepared baking dish and spread out in an even layer, pressing mixture down with your fingers or a spatula. Bake for about 20-25 minutes or until cooked through and golden brown on the edges.
- Let cool before cutting into 16 squares.
Notes
Storage: Store bars in an airtight container at room temperature for 1-2 days. For longer storage, bars keep for up to 2 months in the freezer and thaw in just a few minutes at room temperature.
Ingredients: Use a regular crunchy peanut butter like Jif or Skippy (their Natural varieties work well too). All-natural peanut butters made with just peanuts and salt tend to be runnier, which throws off the consistency and results in crumbly bars. Mini M&Ms are worth seeking out as the regular-sized candies add too much bulk and can cause the bars to crumble when cut.
Serve with: An ice-cold glass of milk is the classic for a reason. For a more indulgent dessert, serve warm with a scoop of vanilla ice cream.
About the Author
Emily Dingmann is a recipe developer, nutrition expert, and founder of My Everyday Table. She specializes in creating easy, healthy recipes that help busy parents feed their families well every single day, without the stress. With a degree in Nutrition and over 20 years of experience, Emily shares family-friendly meals that are practical, nourishing, and full of flavor. Learn more about Emily’s approach to everyday cooking and nutrition here.
Food styling and photography by Loren Runion.
This post may contain affiliate links. They do not add any charge to you, but I will make a very small commission from them. I only link to products I use and recommend. Thank you for your support!