Skip to Content

Monster Cookie Bars

Monster Cookie Bars are packed full of your favorite candy; White Chocolate M&Ms, chocolate  and peanut butter chips baked into cookie bars. These make the perfect treat for your Halloween party, or next fall get together.

Monster Cookie Bars


We are getting closer to Halloween guys! Do you have your costumes picked out?

Will decided to be an astronaut this year {hopefully we can find a costume} and he declared that Drew will be a martian.

So cute, right?

We have been talking a lot about space because Will learns about it in school and has lots of questions, rightfully so. 

He has been enjoying a new app that Mike has on his iPhone.

 You hold your phone up to the night sky and it tells you what stars, planets and constellations are above you.

Seriously, this techy world we live in is amazing.  

I have to admit that I too am very fascinated with space and more recently the pending trip to Mars that will happen in 2022. <– If you don’t know about this google it! Living on another planet? Yup, it is happening!

And now I digress to these ridiculously good Monster Cookie Bars.

The perfect Halloween treat for your family, a party you might be having or your child’s classroom {substitute the peanut butter chips with chocolate chips for nut-free rooms} or just for fun this fall.

Monster Cookie Bars

As part of #TheHalloweenProject I am sharing these Monster Bars alongside all of those other creative, delicious Halloween treats that my fellow bloggers have been sharing. Just to recap so far we have a Spooky Spiderweb Cake from Miranda at Cookie Dough and Oven Mitt,  Candy Corn Cupcakes from That Skinny Chick Can Bake, Bat Cupcakes from Big Bear’s Wife and Bloody Good Cheesecake from Sugar Dish Me.  

If you are planning to make any treats for Halloween we have you covered with this wide array of cute and spooky choices.

Monster Cookie Bars

Today’s Monster Cookie Bars have all kinds of goodies in them including peanut butter chips, chocolate chips and White Chocolate M&M’s. Have you seen White Chocolate M&M’s?

They are new to me. I saw them at the store and knew I had to get them.

First of all the colors are perfect for Halloween and second I think having a little white chocolate in the cookie bars is a nice change.  

When making these you can easily substitute the different candy for a variety of choices.  

If someone can’t have peanut butter you can leave those out and substitute chocolate chips instead.

With the huge variety of M&Ms that are on the shelves these day you can find all kinds of fun options if you want to substitute for the while chocolate variety. Get creative!

Monster Cookie Bars

For today’s Monster Cookie Bars I used Jess’s recipe from Stuck on Sweet for cookie bars as my base and modified from there. If you are looking for other cookie bar recipes you guys have to head to her website.

She is the ultimate baker of all things sweet and she has a variety of really creative cookie bars for you to try!

Monster Cookie Bars

Monster Cookie Bars

Yield: 12
Prep Time: 10 minutes
Cook Time: 25 minutes
Total Time: 35 minutes

Monster Cookie Bars are packed full of your favorite candy, White Chocolate M&Ms, chocolate chips and peanut butter chips and baked into cookie bars. These make the perfect treat for your Halloween party, or next fall get together.


  • 1 cup whole wheat flour
  • 1 1/4 cups all-purpose flour
  • 1/2 teaspoon salt
  • 1 teaspoon baking soda
  • 1 teaspoon cornstarch
  • 2 sticks unsalted butter, room temperature
  • 1 cup light brown sugar
  • 1/4 cup granulated sugar
  • 2 eggs
  • 1 teaspoons vanilla
  • 1 cup peanut butter chips
  • 1 cup chocolate M&M's of your choice {I used a white chocolate Halloween variety}
  • 3/4 cup semi-sweet chocolate chips


  1. Preheat oven to 375 degrees. Line a 9x13 inch baking pan with aluminum foil and spray with non-stick spray.
  2. In a medium bowl mix together the whole wheat flour, all-purpose flour, salt, baking soda and corn starch.
  3. In a mixer using a paddle attachment cream butter and the sugars until light and fluffy; about 2 1/2 to 3 minutes.
  4. Add the vanilla and then the eggs one at a time, continuing to mix, scraping sides of bowl as needed.
  5. With the mixer on low-speed, add the flour mixture in small batches until fully incorporated. Remove the bowl from the mixer and gently stir in the peanut butter chips, M&Ms and chocolate chips.
  6. Spoon the batter into the pan and press the batter into pan.
  7. For softer, gooey bars bake for 25 minutes or for less gooey bars bake for 30 minutes. Let bars completely cool before lifting them out of the pan and cutting.


If there is a peanut allergy substitute the peanut butter chips for chocolate or butterscotch.
I love Jess's idea to use aluminum foil on the bottom of your pan {make sure to still spray it with non-stick spray}. It helps to get those bars out without them sticking. Just make sure you cool the bars completely before you try to remove them.
I subbed whole wheat flour but you can use 2 1/4 cups all purpose flour if you don't want to use whole wheat flour.

CommentLuv badge

50 Recipes To Make With Leftover Halloween Candy - The Farm Girl Gabs®

Wednesday 28th of October 2020

[…] Monster Cookie Bars – A Cedar Spoon […]

Mummy Cookies - A Cedar Spoon

Saturday 12th of September 2020

[…] Monster Cookies Bars […]

38 Frightfully Good Halloween Recipes

Tuesday 18th of September 2018

[…] Monster Cookie Bars by A Cedar Spoon […]

Heather @ Sugar Dish Me

Sunday 11th of October 2015

Julia these turned out SO great!!! I have not tried the White Chocolate M & M's yet but have a bag of candy corn M & M's that might be perfect. I had no idea about the star app! Very cool. thank you so much for being part of #TheHalloweenProject!


Monday 12th of October 2015

Thanks Heather! Thanks for including me. Candy corn M&Ms are perfect for these.


Friday 9th of October 2015

Oh my! These cookies look incredible! My boys will love them! ~Liz


Monday 12th of October 2015

Thanks! My kids loved them.

Skip to Recipe