These Monster Cookie Bars are thick, chewy, ultra ooey-gooey, and packed with peanut butter, oats, M&Ms, and three types of chocolate!
These monster cookie bars are essentially my monster cookie recipe made in bar form and letmetellyou, they’re SO delicious. Packed with oats, peanut butter, and YOUR favorite mix-ins…what’s not to love?!
What are monster cookie bars?
Monster cookie bars are essentially monster cookies, but instead of being portioned out into cookies, they’re baked in a baking dish and sliced into squares. Both monster cookie bars and classic monster cookies are hearty, soft, and chewy, and made with peanut butter, oats, and a variety of mix-ins such as M&Ms and chocolate chips.
Ingredients
These monster cookie bars use pantry staples that you likely have on hand already!
- Unsalted Butter – melted and beat together with the sugar for a soft, chewier texture and classic buttery taste.
- Dark Brown Sugar and Granulated Sugar – both add sweetness. The molasses in dark brown sugar also provides a soft, chewy texture and rich, caramel-y flavor.
- Peanut Butter – use your favorite processed peanut butter such as Jiff or Skippy. I use creamy peanut butter but feel free to use crunchy peanut butter for some added texture, if preferred.
- Egg – binds the cookie bars together so they can hold their shape.
- Vanilla Extract – adds flavor depth and a touch of warm sweetness.
- Old Fashioned Oats – gives the bars their structure and a hearty, chewy texture. You can try using quick oats, but they won’t be as thick and and may not hold up into bars well.
- Baking Soda – gives a little lift so the cookie bars aren’t too dense.
- Salt – balances out the sweetness while also bringing out other flavors in the cookie bars.
- M&Ms – a classic monster cookie mix-in that adds delicious melted chocolate creaminess and candy crunch.
- Other Mix-Ins – I used butterscotch chips, chocolate chunks, chocolate chips, and white chocolate chips.
How to make
These monster cookie bars come together with just 15 minutes of prep!
- In the bowl of your stand mixer, beat together melted butter, brown sugar, and granulated sugar until fluffy.
- Beat in peanut butter, eggs, and vanilla until combined then add in oats, baking soda, salt, M&Ms, and additional mix-ins.
- Transfer the mixture to a greased baking dish lined with a parchment sling then use your hands to press the mixture into an even layer.
- Press in extra toppings, if desired, then bake at 350ºF for 30-40 minutes. Cool completely before removing from the pan, slicing, and serving!
What peanut butter to use
Use a processed peanut butter such as Jiff or Skippy. I prefer to use creamy but crunchy would work as well!
What kind of oats to use
Old-fashioned oats! Their hearty, chewy texture yields the best result. You can use quick-cooking oats but they won’t be as sturdy.
Variations
- Try other mix-ins. Try peanut butter chips, peanut M&Ms, toffee bits, nuts, dried fruits, etc.
- Use crunchy peanut butter. Swap the creamy peanut butter for crunchy for some extra texture.
- Make cookies. Check out my monster cookie recipe instead.
How to store
Leftover monster cookie bars will last for up to a week at room temperature, for up to 2 weeks in the fridge, or for up to 3 months in the freezer.
To enjoy again, bake or warm in the microwave.
– Jennifer
Monster Cookie Bars
Equipment for this recipe
Ingredients
- ½ cup unsalted butter melted
- 1 cup dark brown sugar packed
- 1 cup granulated sugar
- 2 cups creamy peanut butter
- 3 large eggs
- 1 tablespoon vanilla extract
- 4 cups old fashioned oats certified gluten free if necessary
- 2 teaspoons baking soda
- 1 teaspoon salt
- 1 cup M&M’s plus more for topping
- 1 cup additional mix-ins plus more for topping (I used equal parts butterscotch chips, chocolate chunks, chocolate chips, and white chocolate chips)
Instructions
- Preheat oven to 350 degrees F and grease a 9x13 inch baking dish with cooking spray, then line it with a parchment paper sling.
- In the bowl of your stand mixer, beat together melted butter, brown sugar, and granulated sugar until fluffy.
- Beat in peanut butter, eggs, and vanilla until combined.
- Add in oats, baking soda, and salt, then beat again until incorporated.
- Beat in M&Ms and additional mix-ins (butterscotch chips, chocolate chunks/chips, white chocolate chips, etc.).
- Pour into prepared pan, then use your hands to press the mixture into an even layer.
- Press in extra toppings, if desired (this makes it look pretty).
- Bake in preheated oven for 30-40 minutes or until an inserted toothpick comes out basically clean.
- Cool completely before removing from the pan, slicing, and serving!
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Nutrition Information
*Note: Nutrition information is estimated and varies based on products used.
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Jennifer @ Show Me the Yummy
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Jennifer @ Show Me the Yummy
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Jennifer @ Show Me the Yummy
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Jennifer @ Show Me the Yummy