Monster cookies are everything good that there is about cookie-baking and candy-eating. These classic cookies are loaded with peanut butter, oats, chocolate chips, and M&Ms; they bake up soft, chewy, and thick, and are absolutely irresistible!

A white plate piled high with monster cookies.

If you’ve never made these classic cookies, then you're missing out my friends! All of my favorite cookie flavors in one massive cookie. Seriously GOOD, extra thick with a soft texture and unbeatable taste.

They're jumbo sized because they are jam-packed with tons of goodies and when it comes to cookies, bigger is always better!

Ingredients for monster cookies prepped in bowls.

What are monster cookies?

Monster cookies might have earned their name by their creator Dick Wesley, a photographer from Michigan State University, after changing his usual peanut butter cookie recipe. He was out of flour so he used oats and a mashup of other ingredients instead, including 12 eggs and 18 cups of oatmeal, making a HUGE dough.

It’s also believed they’re called monster cookies because they're a combination of so many ingredients, just like the Frankenstein monster! And sometimes they're known as "kitchen sink cookies" because they are loaded with everything but the kitchen sink!

The fabulous thing about these cookies is that they are totally adaptable to your tastes and you can go hog wild in creating the perfect cookie for you.

Peanut butter being stirred into an egg mixture.

The best type of peanut butter and alternatives

I always, always recommend only baking with creamy, processed peanut butter, such as Jif, Skippy, or Peter Pan. Natural-style peanut butter with oil separation is simply too greasy for nearly all baking recipes; using it can result in cookies that spread too much and that can become crumbly.

If you'd like to use a nut butter alternative, see the recipe notes below on some recommendations.

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Chocolate chips and M&Ms in bowl of cookie batter.

Prepping the pans

My baking pans of choice are these rimmed half sheet pans; I have a ton and I use them for everything! And they are perfect for cookies.

I highly, highly recommend using parchment paper to line your baking pans when baking cookies. Greasing cookie sheets will allow excess fat to leach into your cookies, causing them to spread too much and potentially burn on the bottom.

For a brief time, I experimented with silicone baking mats, but over time found that they developed a greasy film that I couldn't get rid of no matter how many times I washed in soapy water or ran through the dishwasher. It was causing the same issues as greasing the pan would, so I stopped using them and went back to parchment paper.

Balls of monster cookie dough on parchment lined baking sheet.

Mix-ins

The fun starts here!

This recipe has the classic M&M and chocolate chips in it, but the possibilities are endless, they could be ANYTHING you want them to be! Here are some suggestions: 

  • Other Chips: Butterscotch, peanut butter, cinnamon, white chocolate chips, toffee bits, etc.
  • Candy: Reese’s Pieces, chopped peanut butter cups, really any other chopped candy bar!
  • Raisins, dried cranberries and cherries: For that extra chewy cookie, plump dried fruit is a great addition.
  • Shredded coconut: This works especially well with the chocolate flavor combination.
  • Rice Krispies: Will give that great extra crunchiness.
  • Chopped Nuts: Add an extra layer of taste and texture.
  • Cinnamon or Nutmeg: For the spice cookie lover!

Monster cookie dough mixed together in glass bowl.

Troubleshooting tips

  • Cookies spread too much – This could be caused by a couple of things. You don’t want to grease the cookie sheet pans, use parchment paper instead. Natural-style peanut butter is too greasy, use creamy processed peanut butter instead.
  • Cookies didn’t spread enough – There are a few things I can think of, the butter may be too warm when added into the batter; so try refrigerating the dough for 30 minutes before baking. Your oven wasn’t at the correct temperature, I recommend an oven thermometer.
  • Cooking falling apart – The most common reasons cookies end up crumbly are using too much flour, be sure to either weigh your flour or spoon it into your measuring cup before leveling. Using the wrong kind of peanut butter may also be the culprit, be sure to see the note about peanut butter.
  • Additional baking tips – You want to be sure you don’t over bake these amazing cookies. The cookies should be just browned around the edges and the centers still look soft and underdone when you take them out of the oven. They will set (perfectly!) as they cool. Let them cool on the baking sheets for a couple minutes and then transfer to a wire rack to finish off cooling.

Make-ahead, storage, and freezing tips

  • Make-Ahead – You can prepare the cookie dough and refrigerate for up to 3 days before baking. When ready, let it sit on the counter for about 30 minutes before scooping and proceeding with baking.
  • Storage – These cookies will keep in an airtight container at room temperature for up to 1 week.
  • Freezing Instructions – These cookies freeze exceptionally well! You can freeze the baked cookies by wrapping them individually in plastic wrap, then place them in a ziptop bag and freeze for up to 3 months. 
  • Freezing the Dough  – You can roll the dough balls and freeze them for up to 2 months. Bake for an extra minute or so.

More of my favorite soft cookies!

A cookie broken in half and the halves stacked together.

If you make these monster cookies and love them, I would so appreciate it if you would take a moment to leave a rating below. Thank you so much! ❤️️

Monster Cookies

Yield: 26 large cookies
Prep Time: 45 minutes
Cook Time: 15 minutes
Total Time: 1 hour
Monster cookies are everything good that there is about cookie-baking and candy-eating. These classic cookies are loaded with peanut butter, oats, chocolate chips, and M&Ms; they bake up soft, chewy, and thick, and are absolutely irresistible!
4.45 (20 ratings)
Print Pin Rate

Ingredients

  • 3 eggs
  • 1 cup (198 g) granulated sugar
  • 1 cup (198 g) light brown sugar
  • 1 teaspoon vanilla extract
  • 2 teaspoons baking soda
  • 1 teaspoon salt
  • ½ cup (113 g) unsalted butter, melted
  • 1½ cups (405 g) peanut butter, creamy or crunchy
  • 4½ cups (446 g) traditional rolled oats
  • ½ cup (60 g) all-purpose flour
  • 1 cup (170 g) chocolate chips
  • 1 cup (209 g) M&M's

Instructions 

  • Preheat the oven to 350 degrees F. Line three baking sheets with parchment paper.
  • In a large mixing bowl, stir together the eggs, both sugars, vanilla extract, baking soda and salt. Then stir in the melted butter and peanut butter, followed by the oats and flour. Lastly, stir in the chocolate chips and M&M's. Let the dough rest (at room temperature) for 30 minutes.
  • Drop the dough by ¼ cupfuls onto baking sheets. Use your fingers to flatten the dough slightly. Baking for 15 to 17 minutes, or until the cookies are a light golden brown. Let cool on the baking sheet for 5 minutes, then remove to a wire rack and cool completely. Store in an airtight container at room temperature for up to 5 days.

Notes

  • Baking Pans - My baking pans of choice are these rimmed half sheet pans; line with parchment paper.
  • Nut Butter Alternatives - You can use other nut butters such as almond butter, cashew butter, etc. as long as they do not have oil separation (see the note above). A great almond butter substitute that works exceptionally well in all baked goods I've tried it with is Barney Butter.
  • Mix-Ins - You can customize these cookies with different baking chips, candy, dried fruit, cereal, nuts, etc. See post above for specific suggestions.
  • Troubleshooting - See post above for solutions to common issues such as cookies spreading too much or too little, being crumbly, and overbaking.
  • Make-Ahead - You can prepare the cookie dough and refrigerate for up to 3 days before baking. When ready, let it sit on the counter for about 30 minutes before scooping and proceeding with baking.
  • Storage - These cookies will keep in an airtight container at room temperature for up to 1 week.
  • Freezing Instructions - Freeze the baked cookies by wrapping them individually in plastic wrap, then place them in a ziptop bag and freeze for up to 3 months. 
  • Freezing the Dough  - You can roll the dough balls and freeze them for up to 2 months. Bake for an extra minute or so.
Calories: 325kcal, Carbohydrates: 40g, Protein: 7g, Fat: 16g, Saturated Fat: 6g, Cholesterol: 31mg, Sodium: 263mg, Potassium: 168mg, Fiber: 3g, Sugar: 27g, Vitamin A: 170IU, Vitamin C: 1mg, Calcium: 42mg, Iron: 1mg

Did you make this recipe?

Leave a review below, then snap a picture and tag @thebrowneyedbaker on Instagram so I can see it!

Author: Michelle Lettrich
Course: Dessert, Snack
Cuisine: American

[Photography by Ari of Well Seasoned]