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Classic Monster Cookies

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When oatmeal and peanut butter cookies collide with M&M’s, chocolate chips and walnuts, the result is a batch of chewy, irresistible Classic Monster Cookies!

I’ve loved these flourless cookies since my mom used to bake up a huge batch back in the 1970’s. She made a large version, about 1/4 cup of dough per cookie; no wonder they were called monster cookies!

Classic Monster Cookies on a white dessert plate

Classic Monster Cookies

I have memories of eating these loaded oatmeal peanut butter cookies right out of the freezer when I was a teenager. Apparently, I haven’t matured much since then! My mom’s classic monster cookie recipe called for 12 eggs, a pound of butter and 18 cups of oatmeal. Scaling down her recipe is must!

Why Are These Called Monster Cookies?

These monster cookies were new on the scene when my mom first baked up that humongous batch using a dozen eggs way back in the 1970’s. Her recipe card called for 1/4 cup of dough per cookie. If those aren’t monster sized cookies, I don’t know what are!

Another plausible explanation is that they are a mishmash of recipes just like Frankenstein was a mashup of a monster! I’m not certain there is a definitive answer. I just know that I loved these peanut butter oatmeal cookies from my first bite!

Classic Monster Cookies piled in a ceramic basket

Tips for Making Monster Cookies

These yummy cookies are a perfect way to get your peanut butter chocolate fix. They freeze great, so don’t worry about the large number a batch makes.  Plus you can shake them up for the holidays by using seasonal M&M’s like I did with these Patriotic Monster Cookies.

Here are a few tips for the best results.

  • This is just half of my mom’s recipe that used 12 eggs and so on. You can easily double it, if you’re feeding a large group, but it also cuts in half perfectly if you’d rather make a reasonably sized batch of 3 dozen cookies.
  • Use quick oats instead of old fashioned oats. The thinner flakes work better in these loaded cookies.  Do not use Instant Oats as they are too fragile.
  • As mentioned, you can make these peanut butter oatmeal cookies with either 1 1/2 tablespoons of cookie dough or 1/4 cup of cookie dough per cookie. Just adjust the baking time.
  • Do not over-bake these cookies. I like them a wee bit underdone so they’re still chewy.
  • PRO-Tip: When measuring out sticky ingredients like peanut butter, honey and corn syrup, spray your measuring cup with non-stick spray and they will slide right out! Game changer!!
  • I like using a cookie scoop so that all the cookies are the same size. If dough starts sticking in the scoop, just clean it and continue.
  • PRO Tip: Often, even when using a cookie scoop, cookies will not bake up into perfect rounds. If this bothers you, take your spatula and tap them into shape when they’re hot and fresh out of the oven.
  • PRO Tip: Another trick to make these bakery shop worthy is to reserve a few M&M’s and chocolate chips to press into the hot cookies to garnish.
  • To freeze, I like to place the cooled cookies in a gallon sized Ziploc freezer bag, remove as much air as possible, then place in the freezer. They can also be layered between sheets of parchment in a covered, airtight container.
  • Generally, cookies can be frozen up to three months, but I’m sure I’ve eaten cookies older than that from my freezer!

More Peanut Butter Treats You’ll Love:

Reese’s Rice Krispie Treats are an amped up version of another childhood favorite. Dorie Greenspan’s Classic Peanut Butter Cookies are divine, as is this Tagalong Dip! If you’re looking for a dinner party dessert, I’d recommend either this Peanut Butter Chocolate Mousse Cake or this luscious Chocolate Peanut Butter Pie.

If you’d like to try making your own peanut butter, try Texan Erin’s detailed recipe. Or how about this Snickers Peanut Butter Brownie Ice Cream Cake from Life Love and Sugar???

Note: This recipe was originally posted in August, 2010. The text and photos were updated in 2019.

Yield: 6 dozen

Classic Monster Cookies

Classic Monster Cookies

Loaded, chewy peanut butter oatmeal cookies

Prep Time 15 minutes
Cook Time 12 minutes
Total Time 27 minutes


  • 2 sticks of salted butter, at room temperature
  • 2 1/4 cups brown sugar
  • 2 cups sugar
  • 6 eggs
  • 2 tablespoons vanilla
  • 2 2/3 cups peanut butter
  • 4 teaspoons baking soda
  • 9 cups quick oats
  • 1+ cup chocolate chips
  • 1 cup chopped walnuts
  • 1/2  pound M&Ms, plus more to garnish


Preheat oven to 350º. Line baking sheets with parchment paper and set aside

Blend butter and sugars. Mix in eggs, then add vanilla and peanut butter.

Mix in soda, then oats, chocolate chips, walnuts and M&Ms.

Scoop out rounded tablespoons of dough and place onto parchment lined cookie sheet. Bake for 10-12 minutes. See note below if you want to make larger cookies. Cool on rack.


The original recipe calls for 1/4 cup dough balls to be baked for 20 minutes if you really want MONSTER cookies.

I like to press a few M&M's into the tops of the cookies as soon as they come out of the oven for a prettier presentation.

Recipe can easily be cut in half if you want to make 3 dozen instead of 6.

2 cookies = 1 serving if you're checking the nutritional info below.

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21 comments on “Classic Monster Cookies”

  1. Liz……I better not show these to my daughter Jackie b/c she’s obsessed with M&M’s. But I guess I can make some up and put in the freezer and have them as treats when her friends come over. Thanks for posting another great recipe, how do you manage to stay so ‘skinny’?????

  2. oh yum! I love Monster Cookies!!!!

  3. Thanks, girls!!!

  4. I still haven’t baked any monster cookies…these look fantastic with M&M!

  5. They look great, breakfast worthy, and ‘flourless’ caught my eye:@)

  6. So good! I think I could eat the whole batch myself — yum!

  7. Freaking amazing! I was looking for a peanut butter oatmeal cookie recipe and so glad I found yours:)

  8. Monster cookies are the best! They are one of my favorites. Thanks for your pro tips- especially about keeping some of the chips to add to the top. They look so much better that way.

  9. Oh boy, our grandson would love these! They look delicious, Liz! Wish I had one now!

  10. I love a good monster cookie! I didn’t know that they were called that because they were so huge!

  11. I bet there’d be plenty of people who’d go crazy for these! M&Ms and peanut butter is a killer combo.

  12. Ohhh!!! I love chewy cookies, big ones like these are so practical. Gee, your mum’s recipe is colossal, makes a ton which is actually not a bad thing at all.

  13. It’s definitely a 1970’s recipe! 12 eggs!?!?! They look totally awesome and I just love all of the inclusions. Saving a few inclusions to decorate the cookies at the end is a real pro tip!

  14. M&Ms are one of the few candies we will actually buy. And I can never resist them! This looks like such a fun recipe — just loaded with goodies (Peanut Butter! Oatmeal!). Good stuff — thanks.

  15. There is something about M&Ms in cookies, it is my total weakness!

  16. OK now I know these cookies, have eaten them (yumm!!!) but I never heard them called monster cookies before. You learn something every day.

  17. These are the kind of cookies that makes everyone smile! Big, chunky and delicious and those pops of color from the M&Ms!

  18. These cookies look great…and yes hard to resist…love all the ingredients in it and the colorful M&Ms…thanks for the recipe Liz.
    Have a great rest of the week!

  19. Liz, you’ll drive the kids wild with these colourful cookies! xoxo 

  20. Your monster cookies make me happy, Liz. Now, if I could just get one with my morning coffee…

  21. Dear Liz, these Monster Cookies are a MUST try! I am convinced that the kids will adore them – I already bought a big bag of M&M’s and peanut butter and hope to try the recipe on the weekend!
    Thank you for sharing the (up-dated) version of your family classic!

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