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 Peanut Butter Oatmeal Cookies since my mom used to bake up a huge batch back in the 1970s. She made a large version, about ¼ cup of dough per cookie; no wonder they were called monster cookies!

Classic Monster Cookies on a white dessert plate.

Why You Must Maketa

  • If you ever need a huge batch of tasty cookies for an event, this recipe is the solution.
  • There is no flour in monster cookies, so it’s perfect for those who can’t have gluten.
  • If you love peanut butter desserts, these cookies will be a hit.
  • They’re loaded with all sorts of delicious ingredients including M&Ms, chocolate chips, and peanut butter.

I have memories of eating these loaded peanut butter oatmeal 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 a must!

Ingredient Notes

  • Kitchen Staples – Sugar, Brown Sugar, Baking Soda, Butter (salted)
  • Eggs – Use large eggs, have them at room temperature for easy incorporation
  • Vanilla Extract – Make sure the label reads real vanilla extract. Don’t use imitation vanilla.
  • Peanut butter – Creamy peanut butter. I use Jif. Don’t use natural peanut butter as the consistency is not ideal for this recipe.
  • Quick Oats – Not old-fashioned oats. You’ll want the softer texture of quick oats.
  • Chocolate Chips – Semisweet
  • Walnuts – Optional. Chopped. If you use them, you may want to toast them briefly in a skillet or the oven to bring out their essential oils (which adds flavor).
  • Regular M&Ms – 1 pound or 16 ounces. Reserve some if you want to garnish after they’re baked. Just press a few onto the top of the cookies shortly after they come out of the oven. Be careful as the pan will be hot!

Recipe Tips 

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 as I did with these Patriotic Monster Cookies.

Here are a few tips on How to Make Monster Cookies:

  • 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 ½ tablespoons of cookie dough or a ¼ cup of cookie dough per cookie. Just adjust the baking time.
  • Cold dough will spread less than room-temperature cookie dough. If you want thicker cookies, just chill the dough before scooping.
  • 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 the 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. Be careful since the baking sheet will be hot. Use a hot pad.
  • PRO Tip: Another trick to make these cookies 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, and then place them in the freezer. They can also be layered between sheets of parchment in a covered, airtight container.
  • Generally, cookies can be frozen for up to three months, but I’m sure I’ve eaten cookies older than that from my freezer!
Classic Monster Cookies piled in a ceramic basket.

Frequently Asked Questions

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 1970s. Her recipe card called for ¼ 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! Or that the size of the recipe is monstrous! I’m not certain there is a definitive answer. I just know that I loved these peanut butter oatmeal cookies from my first bite!

Where Did the Recipe Originate?

I found this info in the comments of another Monster Cookie Recipe: 
“I have the original monster cookie recipe. It was made in the 1930s by the CCC (Civilian Conservation Corps) in the Depression era. The monster name came from the size of the recipe, not the size of the cookie. It has 12 eggs, 2 lbs brown sugar, 4 cups white sugar, 1 tbs vanilla, 1 tbs Karo, 8 tsp soda, 1 lb butter or margarine, and 3 lbs chunky peanut butter. Mix in a very large bread bowl. Add 18 cups of rolled oatmeal. Add 1 lb M&M’s and 12 oz chocolate chips. There is NO flour. I expect the candy was a later embellishment. My 92-year-old husband’s aunts got the recipe when their husbands were in the CCC.”

How Do You Store Monster Cookies?

Store in an airtight container at room temperature for 3-4 days.

Can You Freeze Monster Cookies?

Yes, they freeze beautifully. Put them in a freezer-quality gallon Ziploc bag and keep them in the freezer for 3-4 months. Defrost at room temperature before serving, though I’m happy to eat a frozen cookie!

Can You Freeze the Dough?

Yes, the dough will also freeze well. Scoop out dough balls and place them on a rimmed baking sheet. Place them into the freezer, covered with plastic wrap, for a few hours until they’re frozen solid. Then put the frozen dough balls into a freezer-quality Ziploc bag to store in the freezer. These should keep well for 3-4 months. You can bake the dough balls right from the freezer, but you’ll need to extend the baking time. Or you can defrost the dough balls in the refrigerator and bake.

You May Also Like:

Stay in touch through social media @ InstagramFacebook, and Pinterest. Don’t forget to tag me when you try one of my recipes! And if you love the results, please give it a 5-star rating in the recipe card.

Classic Monster Cookies featured image

Classic Monster Cookies

Prep Time 15 minutes
Cook Time 12 minutes
Total Time 27 minutes
Yield 6 dozen

Loaded, chewy peanut butter oatmeal cookies


  • ½ cup of salted butter, at room temperature
  • 2 ¼ cups brown sugar
  • 2 cups sugar
  • 6 eggs
  • 2 tablespoons vanilla
  • 2 ⅔ cups peanut butter
  • 4 teaspoons baking soda
  • 9 cups quick oats
  • 1+ cup chocolate chips
  • 1 cup chopped walnuts
  • ½  pound M&Ms, plus more to garnish


  1. Preheat the oven to 350º. Line baking sheets with parchment paper and set aside.
  2. Blend butter and sugars. Mix in eggs, then add vanilla and peanut butter.
  3. Mix in soda, then oats, chocolate chips, walnuts, and M&Ms.
  4. Scoop out rounded tablespoons of dough and place them onto a parchment-lined cookie sheet.
  5. Bake for 10-12 minutes. See the note below if you want to make larger cookies.
  6. Cool on rack before serving.


The original recipe calls for ¼ 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.

The 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.

Recommended Products

As an Amazon Associate and member of other affiliate programs, I earn from qualifying purchases.

Nutrition Information:



Serving Size:

2 cookies

Amount Per Serving: Calories: 374Total Fat: 19gSaturated Fat: 6gTrans Fat: 0gUnsaturated Fat: 11gCholesterol: 39mgSodium: 316mgCarbohydrates: 46gFiber: 3gSugar: 31gProtein: 8g


Please leave a comment on the blog or share a photo on Pinterest