This easy recipe for monster cookies is perfect to whip up on a whim or with the kids. Full of oats, peanut butter, chocolate chips, and M&M's everyone loves these cookies. Step-by-step photos help you bake the perfect batch each time!

It's that time of the year where eating copious amounts of cookies is encouraged. AKA my favorite time of the year. These monster cookies are a family favorite for the wonderful flavor and texture. Any dessert that has contrasting textures is a winner in my book, I die over my Dulce de Leche Napoleon for those reasons.
The beauty of this recipe is there is no chilling time required, most of my cookie recipes do require a chill time. Chilling the cookie dough helps prevent the cookies from spreading. Because these cookies are full of oats and peanut butter there isn't a spreading issue.
As with most cookie recipes, I bake half of the recipe and then freeze the rest for a cookie whenever I want. When I bake these from frozen or chilled I do find that I need to bang the pan on the floor halfway through baking to encourage the spreading. But just keep an eye on them, everyone's oven is different.
For another few favorite cookies try my friend Hayley's Potato Chip Toffee Cookies, Jamie's Cuban Shortbread Cookies, or Cheryl's Peanut Butter Blowout Cookies!
Let's get to the monster cookie recipe.
Jump to:
What are Monster Cookies
Monster cookies are a peanut butter-based cookie chock a block full of oats/oatmeal, chocolate chips, and M&M's. These cookies have a great chewy texture and nice crunch thanks to the M&M's.
What are the ingredients
You'll need your standard cookie ingredients here:
- Unsalted Butter. Make sure your butter is completely softened to room temperature. Otherwise, it will not "cream" with the sugars properly.
- Sugar. More light brown Sugar and less granulated sugar helps create a moist and chewy cookie.
- Peanut Butter. You can use creamy or crunchy peanut butter here.
- Large Egg. Your egg needs to be at room temperature, a quick way to warm it up is to place it in a bowl of warm water for 5 minutes.
- Pure Vanilla Extract. Don't bother with the imitation stuff, it is nowhere near the real deal.
- Oatmeal. A classic monster cookie has the chewy and texture of oats. I prefer to use quick-cooking oats but roller/old-fashioned oats work just as well.
- All-Purpose Flour. We don't use a lot of flour here just enough to bind everything together. Some monster cookie recipes don't call for any flour but I prefer it in my cookies.
- Baking Soda. To help raise the cookies and give them their lift.
- Salt. Just a bit is needed in most dessert recipes, it really does help balance everything out.
- M&Ms and Chocolate Chips. Two types of chocolate make these cookies extra special. I often use dark chocolate chips since the M&Ms are milk chocolate!!
Instructions
Preheat oven to 350F/180C and line a cookie sheet with a Silpat liner/ Silicone baking mat. In a large mixing bowl with a handheld electric whisk or in the bowl of an electric mixer beat butter and sugars for 2 minutes on medium speed.
Scrape down the sides of the bowl then add the peanut butter, mix for an additional one to two minutes.
Add in the egg and vanilla extract and mix until fully combined.
In a medium bowl mix together oats, flour, baking soda, and salt.
Add dry ingredients, M&Ms, and chocolate chips to the wet ingredients and mix until just combined.
Be sure not to overmix the batter.
Use a medium cookie scoop and place on prepared baking sheet two inches apart. Add more M&M's and chocolate chips on top of each cookie, if desired.
Bake for 8-11 minutes. Until golden brown and just set. Let cool on sheet for 5 minutes then transfer to wire rack. Store in an airtight container.
Can you freeze the cookies
To freeze unbaked cookie dough:
Scoop the cookie dough into the dough size you want then freeze on a flat surface lined with a silicone mat or parchment paper so they do not stick together. Once the dough is frozen, about 30-60 minutes you can move the cookie dough balls into a freezer-safe plastic bag or container.
To bake frozen cookie dough balls:
Just add an extra minute or two on the bake time. Rotate the pan halfway through, at this point if the cookies have not started to spread down then take the sheet out of the oven and bang on the floor once to encourage spreading. Immediately place the pan bake in the oven to continue baking.
To freeze baked cookies:
Once the cookies are baked let them cool on a wire rack until completely cooled. Place the cookies in a freezer-safe plastic bag or container. To thaw cookies let them sit at room temperature for 30 minutes.
Check out this post on my Cookie Baking Tips
More cookie recipes
If you're looking for a more basic M&M cookie check out my M&M Cookies Recipe.
Or for a no bake cookie recipe check out my Chocolate Peanut Butter No Bake Cookies.
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★★★★★ Please let me know if you make this recipe by leaving a star rating and comment below!
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Monster Cookies
This easy recipe for monster cookies is perfect to whip up on a whim or with the kids. Full of oats, peanut butter, chocolate chips, and M&M's everyone loves these cookies. Step-by-step photos help you bake the perfect batch each time!
- Total Time: 20 minutes
- Yield: 27 Cookies 1x
Ingredients
- 4oz (½ cup) Unsalted Butter, at room temp.
- 150 grams (¾ cup) Light Brown Sugar
- 50 grams (¼ cup) Granulated Sugar
- (4oz) ½ Cup Peanut Butter, creamy or crunchy
- 1 Large Egg, at room temperature
- 2 Teaspoons Pure Vanilla Extract
- 100 grams (1 Cup) Quick Fashioned Oats
- 125 grams (1 Cup) All-Purpose Flour
- ½ Teaspoon Baking Soda
- ½ Teaspoon Salt
- 150 grams (¾ Cup) M&Ms
- 90 grams (½ Cup) Chocolate Chips
Instructions
- Preheat oven to 350F/180C and line a cookie sheet with a Silpat liner. In a large mixing bowl with a hand held electric whisk or in the bowl of an electric mixer beat butter and sugars for 2 minutes on medium speed.
- Scrape down the sides of the bowl then add the peanut butter, mix for an additional one to two minutes. Add in the egg and vanilla extract and mix until fully combined.
- In a medium bowl mix together oats, flour, baking soda, and salt. Add dry ingredients, M&M's, and chocolate chips to the wet ingredients and mix until just combined.
- Use a medium cookie scoop and place on prepared baking sheet two inches apart. Add more M&M's and chocolate chips on top of each cookie, if desired.
- Bake for 8-11 minutes. Until golden brown and just set. Let cool on sheet for 5 minutes then transfer to wire rack. Store in an airtight container for u pto 5 days.
- Prep Time: 10
- Cook Time: 10
- Category: Dessert
- Method: Bake
- Cuisine: American
Keywords: monster cookie recipe, peanut butter oat cookies, easy monster cookie
Brittni Davis says
Going to make these today but I’m making for a large group. I hit x3 to adjust the recipe but the peanut butter measurement never changed. I’m guessing it’s 12 ounces but wanted to make sure. Also, if I’m using peanut butter m&ms instead of regular, should I use less peanut butter? & if I do that, should I use something else instead? I don’t want to mess the texture or consistency up.
Thanks for helping a beginner out!
Elizabeth Waterson says
Hi Brittni, thanks for reaching out! Yes, you are right 12ounces I am so sorry it is not adjusting, I am not sure why, I am going to reach out to support to try and fix it! I wouldn't alter the peanut butter amount if you are using PB m&ms because I love peanut butter! If you wanted just a plain cookie to use with M&MS you could try my M&M cookie recipe! Let me know if I can help with anything else, feel free to DM me on Instagram as I Am quicker to reply there and you can send photos if you have questions! And do report back how you like the cookies! Goodluck! XX Liz