Monster Cookie Bars

With a buttery oatmeal crumble, a soft & creamy peanut buttery filling and plenty of M&M’s, these Monster Cookie Bars will be gone in an instant!

Traditional monster cookies combine M&M’s with chocolate chips, peanut butter and oatmeal….all that goodness packed into one glorious cookie.  I’m pretty sure they named them “monster” cookie, because the bigger the better, right?!

These chewy Monster Cookie Bars are extra delicious, thanks to the ribbon of smooth peanut buttery filling!

Ingredients Needed (Amounts in Recipe Card Below)

• Oats – I prefer the texture of quick oats over old-fashioned oats (aka rolled oats), but you can use either.
• All Purpose Flour 
• Brown Sugar – I prefer brown sugar over white sugar in these; the molasses in brown sugar helps keep them soft and chewy!
• Baking Soda 
• Salt 
• Butter – I use salted butter.
• Creamy Peanut Butter – For best results, I do NOT recommend using natural peanut butter as the texture is unpredictable.
• Egg – I always use large eggs when baking.
• M&M Candies – Regular or mini M&M candies are great!  If you want to boost the peanut butter flavor even more, try using Reese’s Pieces instead!  (Perfect for leftover Halloween candy!)
• Chocolate Chips – I like to use semi-sweet or dark chocolate chips to balance out the sweetness of the filling.  However, you could use a combination of chocolate chips, peanut butter chips and/or white chocolate chips if you prefer!
• Sweetened Condensed Milk – Do not confuse this with evaporated milk! (Very different texture!)

How to Make Monster Cookie Bars

Start by preheating your oven and lining a 9×13-inch pan with parchment paper or greasing with cooking spray.

Then, combine the dry ingredients (oats, flour, brown sugar, soda and salt) in a large bowl or in the bowl of a stand mixer.  

Then add the melted butter, peanut butter and egg; stir until well-combined then mix in the candies and chocolate chips.

Press a little over half of the mixture into the prepared baking pan and set aside.

In a separate bowl, stir together the filling ingredients.  Pour over the bottom oatmeal layer and spread to a smooth layer.

Sprinkle the remaining dough on top and press into the filling a bit.

Bake until golden brown around the edges.  The baking time will vary with different ovens and baking pans, so I recommend starting with less baking time and adding more if needed.  It’s SO important that you do NOT over-bake these chewy bars!

​Make them Festive!!

One reason I love these bars is because I can make them festive for almost any holiday using different colorful M&M candies (just like in my M&M Cookie Bars!).  They’re a huge hit no matter what time of year it is!

Try these warm with a scoop of vanilla ice cream – highly recommended!!!

Can I Make these Monster Bars Gluten Free?

Yes!!!  You’ll need to switch out the wheat flour for an all purpose 1-to-1 gluten free flour.  Also, if you’re planning to serve these to someone with celiac disease, you’ll want to make sure the oats are certified gluten free and the peanut butter is free of bread crumbs! 🙂

How do you Store Monster Cookie Bars?

I recommend letting them cool on the counter before cutting. Cover them with plastic wrap or store them in an airtight container at room temperature for up to 5 days.  You can also freeze these for up to 2 months.

Other Delicious Cookie Bars