Chewy cookies with a slightly crispy edge, made of oatmeal, peanut butter, and just enough chocolate. Make a generous batch to share!

monster cookies with peanut butter pieces

Looking for a simple, last-minute Halloween treat you can bake up over the weekend? Look no further! These monster cookies are easy, festive, and – consider yourself warned – completely addictive. I literally cannot stop eating them, even though I really need to.

Before making these, I did not realize that “monster cookies” specifically refer to oatmeal peanut butter concoctions that also include chocolate chips and M&Ms. (I mean, that is a mouthful, so I can see why someone coined a shorthand for it.) I have read a few stories of monster cookies gone wrong – think too much peanut butter, too many oats, or just too much going on overall. However, this version is to die for. They are slightly less sweet than some other recipes, and although I was personally a bit skeptical because there are so very many oats in the recipe, rest assured it all came together beautifully.

My inexplicable urge to make these “seasonal” led me to swap out M&Ms for Reese’s Pieces (the miniature ones designed for baking), since that is what I could find in Halloween-like colors, and man oh man, was that ever a happy switch. The overall peanut butter flavor really stands out thanks to the extra filling and crunch that the pieces add. Plus, maybe I am a bit of a nerd, but I’ll be honest, I find them adorable.

Be aware that the recipe makes a gargantuan batch. Depending on how generously you scoop out your dough*, you may end up with a normal number of very large cookies, or a huge number of normally-sized cookies, but either way, you are going to have a lot of dessert. Admittedly these are not the healthiest things to have in large quantities, but I am a major proponent of all things in moderation, and also a major proponent of sharing. So I strongly recommend that you bake the full batch, eat a few, visit your neighbors, take some to work on Monday, say boo!, and spread the love.

*On a side note, does anyone use a cookie dough scoop for measuring out and forming dough balls on the baking sheet? What kind? Do you like it? I’ve toyed with getting a set of scoops for quite awhile, but hesitate because the kitchen is already pretty full and I’m wary of adding tools that serve a limited purpose. Thoughts? Are they worth it?  

Monster Cookies with Peanut Butter Pieces
Yields about 4 dozen medium-sized cookies

1/2 cup all-purpose flour
1 tbsp. baking soda
pinch of salt
5 3/4 cups old-fashioned oats
3/4 cup (1 1/2 sticks) cold unsalted butter, cut into cubes
1 1/2 cups light brown sugar, firmly packed
1 1/2 cups granulated sugar
5 large eggs
1/4 tsp. light corn syrup
1/4 tsp. vanilla extract
2 cups creamy peanut butter
1 cup semisweet chocolate chips
1 cup peanut butter candy pieces

In a large bowl, whisk together the flour, baking soda, and salt. Add the oats and stir until the mixture is evenly combined. Set aside.

In the bowl of an electric mixer fitted with the paddle attachment, cream the butter cubes until they are smooth and pale in color. Add the sugars and mix on low speed until everything is just incorporated. Add the eggs one at a time, scraping down the sides of the bowl and beating after each addition. Add the corn syrup and vanilla, mix again just until incorporated, and scrape down the sides of the bowl one more time.

Add the peanut butter and mix on low speed for 20-30 seconds. Incorporate the oat mixture in three additions, mixing each on low speed just until the dough returns to an even consistency. Fold in the chocolate chips and candy pieces using a spatula or wooden spoon. Cover the bowl tightly and refrigerate for at least five hours or overnight.

When ready to bake, preheat the oven to 375 F and prepare baking sheets with silicone liners or parchment paper. Form dough into balls between 1-2 tbsp. each, and space about 2 inches apart on the baking sheets. Using your hands, shape each cookie into a smooth ball. (Rolling the dough into balls is not strictly necessary, but I found it gave the baked cookies a prettier, more even appearance. Alternatively you could use a dough scoop or ice-cream scoop for this step.) 

Bake about 12 minutes, rotating the pans halfway through, until cookies are lightly golden. Let cookies cool on the pan for about 8 minutes, then transfer to a wire rack to cool completely. Store at room temperature in an airtight container.

Source: Barely adapted from Baked: New Frontiers in Baking