Cinnamon Oatmeal Monster Cookies

Cinnamon Oatmeal Monster Cookies |

I’ve been making Monster Cookies since I was a kid (like 8 years old – really – I remember pulling out a bowl almost as big as me to mix up 18 cups of oatmeal!) Most of the original Monster Cookies recipes are GIANT recipes – thus the name.

I’ve adapted this recipe significantly over the years. Our favorite recipe tweak has been to add leftover Halloween candy! Not only do 3 Muskateers get gooey in the oven – and Milky Ways become melty caramel, but Tootsie Rolls become totally edible! (I’m not a Tootsie Roll fan unless it’s in Monster Cookies!) Tootsie Rolls become chocolate melty caramel!

My kids and I have experimented and found the very best Halloween candy to mix into these cookies:

🍫 Butterfingers melt in the oven into golden crispy toffee!

🍫 3 Musketeers turn into ooey-gooey pools chocolatey nougat.

🍫 Surprisingly, Tootsie Rolls melt into the best chocolatey caramel!

🍫 Snickers…well, melted caramel peanuty 🥜 Snickers, need we say more?!

But the best part of adding Halloween candy to cookies it makes some of our gobs of Halloween candy disappear – PLUS it makes that candy into a somewhat ‘healthier’ treat! The addition of whole grain oats, good-fats packed peanut butter makes a snack that’s now got the added nutrition of some fiber (oats) and protein (peanut butter).

Here are some of the other healthier changes I made:

  • Cut back on the white sugar and brown sugar.  But they are still plenty sweet! I also kept both brown and white sugar as that ensures that the cookies stay soft and chewy for almost a week
  • Cut the fat and swapped out some butter for canola oil.  With the addition of oil, the amount of sugar and fat can be reduced without sacrificing the incredible chewy texture that makes these cookies a favorite.
  • Removed the flour. These cookies are now gluten-free – for all your gluten-free friends. Just make sure to use gluten-free mix-ins if you’re delivering them to friends.
  • Added cornstarch. Yes, only the small 1 1/2 teaspoon amount makes a BIG difference in the texture. Again, we’re looking for puffy, chewy here. The cornstarch does need a bit of time to do its magic. So chill the finished dough for a few minutes
  • Chill for at least 15 minutes. This time in the refrigerator has two purposes. First, it helps keep the cookie dough from spreading too quickly on the sheet pan in the oven. We like puffy, thick cookies, not flat pancake cookies. Secondly, the rest time in the fridge helps the cornstarch do its magic. Chill for 15 minutes before scooping up the first baking sheet of cookies. Then, chill between scooping out each batch.
  • Add the MOST FUN mix-ins! Big wads of leftover Halloween candy to add to the cookie batter are the best.

Cinnamon Oatmeal Monster Cookies |


Cinnamon Oatmeal Monster Cookies

These chewy oatmeal cookies are popularly called monster cookies – and are a great way to use up leftover Halloween candy. I’ve made them a little healthier so they are great for after-school snacks.

  • Author: by Serena Ball, RD
  • Yield: About 4 dozen 1x


  • 2 cups brown sugar
  • 1/2 cup granulated sugar
  • 1/4 cup butter
  • 1 cup peanut butter
  • 4 eggs
  • 1/4 cup canola oil
  • 2 teaspoon vanilla extract
  • 6 cups old-fashioned oats
  • 2 1/2 teaspoons baking soda
  • 1 1/2 teaspoon corn starch
  • 1 teaspoon cinnamon
  • 1/4 teaspoon table salt
  • 2 cups chopped chocolate, peanut or caramel Halloween candy (Tootsie Rolls work especially well) OR 1 cup chocolate chips plus 1 cup M&M’s


  1. Cream together sugars, butter, and peanut butter. Beat in eggs, oil, and vanilla. In a separate bowl, combine oats, baking soda, corn starch, cinnamon, and salt; add oat mixture to egg mixture and stir well ith a wooden spoon. Fold in candy.
  2. Chill dough in the refrigerator for 15 minutes. Then chill between scooping out each batch of cookies.
  3. Preheat oven to 350 degrees. Using an ice-cream-scoop spoon dough onto a greased cookie sheet. Bake for 10-15 minutes until tops are no longer wet and cookies begin to color golden brown.
  4. Cookies freeze well.


The original Monster Cookie recipe is ‘monster,’ it contains 18 cups oatmeal, 2 pounds of brown sugar, and 1 pound of butter. I cut this recipe in thirds – but also drastically cut the sugar and butter proportions. They still come out chewy and delicious and peanut-y!

Did you make this recipe?

Share a photo and tag us — we can't wait to see what you've made!


We’re Serena & Deanna, two dietitians who love food as much as you do!  

We're also moms and business owners who share our family recipes, healthy kitchen hacks and nutrition adventures while keeping it real in the kitchen with you.

We’re so glad you’ve stopped by!

Hungry for More?

Don’t miss a single delicious, nutritious, food-lovers recipe! For exclusive Healthy Kitchen Hacks and incentives provided only to our subscribers, sign up here to receive our weekly e-newsletter.


Sign up with your email address to receive news and updates.
Type your custom success message here...