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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. 5 stars
    SO GOOD! I was a bit worried based on some comments that they turned out cakey but I followed the recipe exactly and mine were soooo thin and spready and crispy. YUM.

  2. 5 stars
    Love these and they go over very well every time I share at a gathering. Mine don’t spread either like some have mentioned, but I chill before baking and tend under bake them a little. But I like a gooier cookie, so it works out well.

  3. Long time fan of this page but been having such a hard time when it comes to the baking recipes. Every time we make cookies and follow the instructions diligently they come out so thick and cake-like. When making other cookie recipes from other sites we don’t have this problem…. just not sure what’s going on because they don’t appear to be that style in the insta/website posts. Help!

    1. Hi Jenna! I am sooo sorry about that! Hmm I would maybe recommend using a little less flour and try underbaking a bit? xT

  4. Hey, Tieghan! I am super excited to try these, but I’ve been unable to find the Halloween-colored M&M’s. I did find some s’mores-filled ones; do you think I could substitute those?

    Thank you!

  5. 3 stars
    It was weird..I think there might’ve been too much baking soda as my cookies had a slight bitter taste…it could’ve been from the pretzels as well I’m not sure. They’re decent 🙂

  6. 5 stars
    Recipe is so good! How should you store the cookie dough if you don’t make all the dough at once?

    1. Hi Erin,
      Thanks for trying this recipe and sharing your feedback, sorry to hear it wasn’t enjoyed. Anything you may have adjusted in the recipe or anything that I can help with? xx

  7. 4 stars
    I followed the recipe exactly except I mixed the flour, baking soda, baking powder salt and oatmeal together and then added it to the creamed butter and sugar. That is the part of the recipe that you should not overmix.
    Also make sure your butter is at room temp. If you do this the cookies turn out perfectly.

    1. Hey Jayne,
      Fantastic!! Thanks so much for sharing your feedback and giving this recipe a try, I am so glad it turned out well for you! Have a great weekend:)

  8. 5 stars
    I was so happy how these came out! I may have just ate the last one for breakfast. HUGE hit at our neighborhood Halloween party. Great taste and texture

  9. 3 stars
    After reading the reviews, I made sure not to over mix, but in the end I had the same results as everyone else. The cookies turned out thick and did not spread, even with me flattening them out. Pretty to look at, but I wasn’t crazy about them.

  10. 4 stars
    My grandson and I made the great cookies together but we ran out of eyeballs. My clever grandson dribbled melted chocolate over white M&M’s, making new eye balls. They looked great and the cookies were delicious. Thanks for the recipe.

    1. 2 stars
      I read thru comments b4 making & was extra cautious to do everything right. Like most posts, these didn’t flatten or spread. They are dry and bland. Something is def off with this recipe as written. Super disappointed.

      1. Hi Lisa,
        Thanks for trying the recipe a try and sharing your feedback, so sorry to hear they weren’t enjoyed. All of the instructions are correct:) xx

  11. 4 stars
    My children and I had a great time making these this morning for Halloween. They are very eye-catching and yummy, but they came out cakey and not crinkly like your pictures. If overmixing does this, I am definitely guilty. I think next time to avoid this, I’d whisk the dry ingredients well before adding them to the wet, and I’d include the mix-ins with the dry stuff. Thanks for a fun and delicious activity for our family. 🙂

    1. Hi Mandie,
      Thanks so much for making this recipe and sharing your feedback! Yes, over mixing can be a cause of a cake-y cookie:) So glad they were enjoyed! xT