Monster Cookie Bars are a quick and easy big batch dessert recipe that can be made in one bowl! They are just like a giant Monster Cookie. Loaded with chocolate chips and M&Ms. This bar recipe is soft, chewy and always a hit. Perfect for potlucks, bake sales and more!
The only thing better than cookies are cookie bars! I don’t know about you, but skipping the step of rolling out cookie dough and just baking it in a pan instead is is my kind of baking. When I need a last-minute dessert for a party or potluck, more often than not I make a batch of cookie dessert bars like these monster cookie bars.
These cookie bars pretty much have all of my favorite cookie things – peanut butter, oats, and chocolate all baked up together in a warm and gooey dessert. You can make a huge batch of these cookies in about 20 minutes, start to finish… yes, you read that right!
If you’ve been following this blog for long, you know how I love my cookie bars! These easy cookie bars are loaded with M&Ms and chocolate chips just like regular monster cookies, but so much easier. It’s as easy as mixing the dough and baking in a big pan! Just like my pizza bars, sugar cookie bars and banana bars these are great when you need cookies for a crowd.
Why You’ll Love Monster Cookie Bars
- No flour monster cookie bars are gluten free! Just make sure the oats you purchase are gluten free, and all the rest of the ingredients as well.
- It’s an easily shareable treat. Cut into even squares or rectangles and you’ve got a tasty sweet that you can bring to parties and get togethers.
- These tasty cookie bars are great to make ahead and store for a day or two until needed.
Ingredients for Monster Cookie Bars
- Quick oatmeal – Quick oats are the easiest way to get a soft and chewy texture in these cookie bars.
- Brown sugar – Brown sugar gives these cookie bars a rich and caramely flavor.
- Chocolate chips – I typically grab semi-sweet chocolate chips when making cookies, but dark chocolate and milk chocolate are just as good! There’s never a bad choice when it comes to chocolate.
- Butter – Allow butter to soften at room temperature so that it more easily incorporates with the rest of the ingredients.
- Eggs – Eggs will help bind the cookie ingredients together and make a cookie bar that won’t fall apart.
- Vanilla – Vanilla extract goes so well will in cookies that have brown sugar and chocolate. It’s a lighter note among the rich flavors!
- Peanut butter – Use creamy peanut butter for best results.
- Corn syrup – Using corn syrup will help sweeten them and give them that dense, chewy structure.
- Baking soda – Even these no flour monster cookie bars still need a rising agent to give them a fluffy texture!
- M&Ms – You can’t have monster cookies without M&M’s.
How to Make Monster Cookie Bars
Spray a 18×13 baking pan with non-stick cooking spray and set it aside for later. Preheat the oven to 350 degrees Fahrenheit.
Beat together butter and sugar in a large mixing bowl with an electric hand mixer or stand mixer.
Once creamed together well, add eggs, vanilla extract, corn syrup, and baking soda and mix until just combined. Stir in the peanut butter with a large spoon or silicone spatula, then add oatmeal.
Add chocolate chips to the cookie bar dough and gently mix them in.
Spread the mixture onto the previously prepared baking pan, and then sprinkle M&M’s over the top and gently press them into the dough.
Place them into the oven and bake for 15 minutes until soft and chewy. The bars may not look fully done, but they’ll firm up a bit as the cool!
How to Store Leftover Monster Bars
Place leftover bars into an airtight container with parchment paper between layers and store at room temperature for 3-4 days.
FRIDGE: To make this treat last a bit longer, store leftovers in the refrigerator for up to a week.
FREEZER: They can be frozen too! Wrap each bar individually in plastic wrap or place them in an airtight container. Store in the freezer for up to 3 months. Allow to thaw before eating.
Can I use old fashioned oats instead of quick oats?
Quick oats is a faster cooking oatmeal, which is why it is important to use them in this recipe. Old fashioned oats and steel-cut oats will give the these dessert bars a different texture.
However, if you don’t have quick oats you can break down some old fashioned in a food processor by pulsing them a few times. They should work pretty well after that!
There’s tons of tasty things you can add to monster bars, or use as a substitute for the listed ingredients. Reeses pieces are a great addition or substitute for the M&Ms. Add more candy like heath bar pieces, chopped peanut butter cups, and any other chocolatey candy.
Chopped nuts like pecans, walnuts, and peanuts are a great crunchy addition as well!
- Wait until the cookie bars are completely cooled before you slice them. The cookies may fall apart if you slice them while they’re warm.
- When you press the dough into the pan, press it just enough but not too hard, otherwise your cookies will be too dense. Use a light hand for this step!
- The cookies don’t have to bake long and as I mentioned earlier, they won’t look done when you pull them out of the oven. But don’t over-bake them. They will finish cooking on the hot pan and will set just fine!
This easy monster cookie bars recipe makes the best twist on a classic treat!
More Dessert Bars You’ll Love
- No Bake Peanut Butter Cereal Bars are perfectly ooey gooey and delicious!
- These Knock You Naked Bars are a cookie bar with an amazing layer of gooey caramel stuffed in between the layers with a hint of peanut butter.
- Banana Bars are topped with cream cheese frosting and are so soft and tender.
- My Caramelitas are super easy to make and absolutely addictive!
- ½ cup butter softened
- 3 eggs beaten
- 1 cup white sugar
- 1 teaspoon vanilla
- 1 teaspoon corn syrup
- 2 teaspoon baking soda
- 1 cup brown sugar packed
- 1 ½ cups peanut butter
- 4 ½ cups quick oatmeal
- 6 ounces chocolate chips
- 6 ounces M&M's
- Preheat oven to 350 degrees Fahrenheit. Spray a 18×13 inch baking pan with non-stick spray. Set aside.
- In a large mixing bowl or bowl of a stand mixer, add butter and sugars. Beat together until creamed.
- Add eggs, vanilla, corn syrup, and baking soda and mix until just combined. Sir in peanut butter and mix until combined then stir in oatmeal and mix.
- Add chocolate chips and gently mix by hand until combined.
- Spread into a greased 18 x 13 inch pan. Sprinkle M&Ms on top of batter in a pan and gently press into the dough.
- Place in the oven and preheated at 350 degrees Fahrenheit for 15 minutes for a soft, chewy bar. They will not look done, but will cook as they set.
- Mix it up and uses peanut butter chips and Reese’s Pieces for a peanut butter Monster Bar!