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Boooo! Halloween Monster Mash Cookies! Festive, easy, sweet, and gravely spooky! Homemade chocolate chip cookies, made with oats, pretzels pieces, plenty of chocolate chunks, spooky Halloween M&M’s, and crazy candy eyes. There’s nothing not to love about these sweet chocolate cookies with a little salty pretzel crunch. Each bite is slightly crisp on the edges but soft and gooey in the center with melted chocolate throughout.

Halloween Monster Mash Cookies |

Ahhh! I am so happy to share these! In all honesty, I’ve wanted to make these fun, super yummy cookies for months. Actually, since almost a year ago when I made my much loved Christmas Monster Cookies. It was then that I knew that Halloween Monster Cookies needed to follow.

I’m not sure which cookie I love more. Both are unique, special, and melt-in-your-mouth delicious.

I know, I’m such a dork, but nonetheless, I just love how fun Halloween can be!

I wanted to share them very early in the Halloween season. My hope is that you can bake them up for all of your Halloween needs. Parties, school functions, and even just as a fun cookie to bake on a random weekday. Whatever you bake them up for, they require almost no effort!

Halloween Monster Mash Cookies |

Spooky details

Start off by gathering all of your ingredients. You’ll need the basics: salted butter, dark and light brown sugar, flour, baking powder, baking soda, and salt – the usuals.

You’ll also need the stir-ins, they’re the most important element of these cookies. You’ll need old-fashioned oats, salted pretzel twists, semi-sweet or dark chocolate chunks, and candy eyes. Plus plenty of spooky Halloween M&M’s, which, of course, make these cookies.

Simply mix up the dough, bake each cookie off, and then enjoy!

Halloween Monster Mash Cookies |

We love to eat these cookies warm, just out of the oven. They’re just the right type of gooey delicious cookies to pull out, slightly cool, and indulge in.

One thing that’s important to note, is that these cookies do spread, so don’t stress on that. Because of this, they’re meant to have slightly crisp edges and perfectly soft gooey centers, just like in the photos. My favorite type of cookie. Everyone has really been loving these cookies, they’re definitely an Oslo favorite!

Halloween Monster Mash Cookies |

If you want a bit of a thicker cookie, simply omit the additional egg yolk and use only two eggs. As a result, this will give you a thicker cookie without as much spreading.

To get the M&M’s to really pop, I like to add in a few just before the cookies finish baking completely. This way each cookie has a bit of the festive M&M’s right on top.

Excited to see you all bake these up this month! What’s incredible about these cookies is just how easy they are. So have fun with them and enjoy every shamefully sinful spooky monster bite!

Halloween Monster Mash Cookies |

Looking for other Halloween cookies? Here are my favorites: 

“I put a Spell on You” Poison Apple Martini

Black Widow Peanut Butter Bars

Hocus Pocus Spellbook Brownies

Spooky Halloween Pretzels

BOO! Chocolate Peanut Butter Bars

Milk Chocolate Stuffed Jack-O’-Lantern Cookies

Black Cat Pumpkin Cupcakes

Roly Poly Pumpkin Cookies

Lastly, if you make these Halloween Monster Mash Cookies, be sure to leave a comment and/or give this recipe a rating! Above all, I love to hear from you guys and always do my best to respond to each and every comment. And of course, if you do make this recipe, don’t forget to tag me on Instagram! Looking through the photos of recipes you all have made is my favorite!


Halloween Monster Mash Cookies

Prep Time 20 minutes
Cook Time 15 minutes
Total Time 35 minutes
Servings: 20 cookies
Calories Per Serving: 311 kcal

Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed.



  • 1. Preheat the oven to 350° F. Line a baking sheet with parchment paper.
    2. In a bowl, beat together the butter, brown sugar, and vanilla until combined. Beat in the eggs and 1 egg yolk, 1 at a time, until combined. Add the flour, baking soda, baking powder, and salt. Beat in the oats.
    3. Fold in 1 cup of the M&M's, the pretzels, and chocolate chips.
    4. Roll the dough into 1/4 cup size balls. Place 3 inches apart on the prepared baking sheet.
    5. Bake for 8 minutes, then rotate the pan and bake another 2 minutes. Pull the pan out and push the remaining M&M's and candy eyes into the cookies. Bake 2-3 minutes. Remove from the oven and let the cookies cool on the baking sheet. They will continue to cook slightly as they sit on the baking sheet.
    6. Eat warm or let cool and store in an airtight container for up to 4 days. 
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Halloween Monster Mash Cookies |

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  1. Like a few other commenters, my cookies didn’t really spread – I was careful to measure the flour exactly and tapped the cookie sheets on the counter a few times throughout the baking process, but no luck. My guess is that I ended up over-mixing the dough to get all the fillings evenly distributed. I also didn’t chill the dough before baking it today, although I froze half, so I’ll see if the frozen ones end up any different.

    That being said, they’re still delicious cookies. My bf even gave them the stamp of approval, despite the fact that he doesn’t like pretzels.

    1. Hi Mara,
      Thanks so much for trying this recipe out and sharing your feedback! So glad they were enjoyed! You could gently press the dough down with your palm before baking for a flatter cookie. I hope this helps! xT

  2. 5 stars
    Made these tonight for our Halloween party! Delicious! Next time I think I will crush up the pretzels better and sprinkle with sea salt because I like my chocolate chip cookies on the salty side!

    1. Hey Madalyn,
      Happy Monday! 👻 I am thrilled to hear that this recipe was a winner, thanks so much for making it! Happy Halloween! 🎃

  3. Still turned out pretty good but were dry and cakey (even though I followed the recipe exactly). Didn’t look like the pictures as they were gooey, crispy or flat.

    1. Hi Jay,
      Thanks for giving this recipe a try and sharing your feedback, sorry to hear these were dry for you. Was there anything you may have adjusted? What kind of oats did you use? Is it possible the dough was over mixed? Let me know how I can help! xT

  4. These cookies are wonderful and so cute! I can’t wait to share them! Mine didn’t spread as much as yours but they did spread some. I think they are perfect! Thank you again for another fabulous recipe!!

    1. Awe thanks so much Robin!! I am so glad this recipe turned out well for you, thanks for giving it a try! Happy Halloween! 👻

  5. 5 stars
    I just made these – did the half brown butter method from your other cookie recipes and added in some peanut butter chips along with the chocolate chips and they’re delicious! I also forgot the pretzels but I think they’re great!

    Thanks for the recipe, it’s a definite winner!

    1. Hey Rhi,
      Happy Sunday! 🎃 So glad to hear that this recipe was a hit, thanks a lot for making it and sharing your feedback! xx

    1. Hi Emily,
      So sorry to hear you did not enjoy this recipe. Was there anything you may have adjusted? Could the dough have been over mixed? Please let me know how I can help! xT

  6. 4 stars
    I made these today but mine didn’t look as good as yours. One, I couldn’t find plain Halloween m&m’s so I had to use a slightly filled, bigger m&m. Two, mine didn’t spread as yours did but still looked good. They are a pretty yummy cookie though!

    1. Hey Cindy,
      Happy Sunday! 🎃 So glad to hear you enjoyed, thanks a lot for making it and sharing your feedback! I would try tapping your baking sheet on the counter for a flatter cookies next time. xx

  7. Cute but they did not spread! Too many oats I think and with the pretzels to dry. Next time I would do 1 cup instead of 2.

    1. Hi Sydney,
      Thanks for giving these cookies a try and sharing your feedback, sorry to hear they did not spread for you. Was there anything you may have adjusted in the recipe? Did you try tapping your baking sheet on the counter? Let me know how I can help! xT

    2. My cookies didn’t spread either. I would like to know what I should change. I followed the instructions. Mine turned out puffy

      1. Hi Angie,
        Is it possible your dough was over mixed? Did you chill the dough at all? You could try gently pressing the dough down with your hand before baking. I hope this helps! xx

  8. Could I substitute the all-purpose flour for coconut or almond flour? Do you think it would mess up the consistency of the cookies?

    1. Hi Yesenia,
      I would recommend using a gluten free flour blend like Bob’s Red Mill for best results! I hope this recipe turns out well for you! xx

  9. 4 stars
    I’m going to make these again but going to take out the oats… I think it made them a little dry. Otherwise, these were super fun to make.

    1. Hi Jen,
      Thanks for making these cookies! If you are going to omit the oats, I would add 1/3 cup of flour, I haven’t tested this! Let me know how they turn out! xT

  10. 5 stars
    Made these this afternoon with my 2 year old and they turned out amazing. So cute and so yummy! I’m going to save some for our Halloween party this weekend too!

    1. Hey Kelly,
      Happy Friday!🎃 I am delighted to hear that this recipe was enjoyed, thanks for trying it out and sharing your review! xx

  11. These are delicious!! And super easy to make. Only complaint is I ate way too many in one sitting when they came out of the oven!

    1. Hi Caroline,
      Happy Friday!🎃 I am delighted to hear that this recipe was enjoyed, thanks for trying it out and sharing your review! xx