Soft-Baked Monster Cookies.

Super soft and thick peanut butter cookies with oats, chocolate chips, and M&Ms. 

Monster Peanut Butter Cookies - the best monster cookies you'll ever make! @sallybakeblog

“Monster Cookies” are peanut butter oatmeal chocolate chip M&M cookies. For as much as I love peanut butter and oatmeal cookies, it’s quite surprising to see no basic peanut butter oatmeal cookie recipe in my archive.  To be honest, the reason I’ve never shared one with you is because it’s taken me almost 3 months to develop one I’m proud enough to publish. Too flat, too puffy, falling apart, rock hard, too dry, and too sweet peanut butter oatmeal cookies have all made their way in and out of my kitchen lately.  But not this one.  Oh my heavens.  I’ve finally found that “perfect” one.  I am so excited to show you!

As I mentioned above, “monster cookies” are peanut butter oatmeal cookies stuffed to the brim with colorful M&Ms and chocolate chips.  Today’s recipe is unlike most traditional monster cookie recipes though.  It’s more like a peanut butter cookie with oats, rather than an oatmeal cookie with peanut butter.  Still with me?

Also putting these monster cookies apart from the rest is that they are soft-baked. My favorite cookie term! Soft, tender, chewy, and moist in every bite.  Quite unlike the crunchy hard peanut butter cookies you are used to. And finally, my version is stuffed with a variety of M&Ms. Peanut Butter M&Ms, classic M&Ms, and mini M&Ms all paid a visit to my monster cookie dough.

Monster Peanut Butter Cookies - the best monster cookies you'll ever make! @sallybakeblog

Also good to know ahead of time is that my recipe doesn’t make 5-6 dozen cookies like most monster cookie recipes I’ve seen out there that use 3 eggs, 4 cups of flour, 4 cups of oats, 1 pound of butter, etc.  Rather, my recipe uses a fair amount of ingredients and yields just 2.5 dozen medium-sized cookies, so they aren’t actually “monster” in size, but feel free to make them larger.  Oh and bonus: it can all be mixed up in ONE bowl.

It’s an easy, manageable, and quick recipe! One thing I will note: lease use quick oats here. Why? You need the slightly finer size from the quick oats in order to give the cookies a more uniform texture.  Quick oats will act more as a binder in this recipe than whole oats would, since the consistency is more powdery and the oats are smaller in size.  I actually did not have quick oats at the time, so I ground up my oats in a food processor for a quick 10 seconds to break them down.

Like I mentioned, this is a quick cookie recipe! There is no dough chilling needed for these cookies! The dough is quite manageable as is. However, should you bake these cookies with a thinner peanut butter or on a particularly humid day, be sure to chill for up to 30 minutes in the refrigerator.  Cookie dough can be testy. Go by how your dough feels. If it’s too sticky, chill for 30 minutes. If not, just bake.

Helpful tip: the cookies spread just slightly while baking, so you’ll need to press them down a bit a bit with the back of a spoon once you remove them from the oven.  That’s what gives the cookies their crinkled tops.

Let’s discuss their texture. Wow. I baked these on a Saturday and by Wednesday, they were STILL so soft. Why did they last that long? I forgot I had one sitting around in a little baggie (whoops). So, yes. These cookies remain exceptionally soft for days and days. I also found that their peanut butter flavor is enhanced after day 1, too. Just wait until you taste these!

The oats make them unbelievably chewy, the M&Ms give them a pop of color, and we obviously love the combination of chocolate chips and peanut butter. And I love how thick they are! Even after slightly pressing down after they come out of the oven, the cookies are still so thick and hearty.

Monster Peanut Butter Cookies - the best monster cookies you'll ever make! @sallybakeblog

In a world where there can never be too many peanut butter cookies, I’m happy to have a peanut butter oatmeal cookie I can use again and again.  Especially ones that took me a several batches to develop and perfect. It was worth the wait!

Follow me on Instagram and tag #sallysbakingaddiction so I can see all the SBA recipes you make! ♥

Soft-Baked Monster Cookies

The best monster cookies ever.


  • 1/2 cup (1 stick or 115g) salted butter, softened to room temperature*
  • 1/2 cup (100g) packed light brown sugar
  • 1/4 cup (50g) sugar
  • 3/4 cup (185g) creamy peanut butter
  • 1 large egg
  • 1 teaspoon vanilla extract
  • 1/2 teaspoon baking soda
  • 1 and 1/4 cups (160g) all purpose flour (measured the correct way)
  • 1/2 cup (40g) quick oats*
  • 3/4 cup (150g) M&Ms (any size or variety)
  • 1/2 cup (90g) semi-sweet chocolate chips


Preheat oven to 350F degrees. Line baking sheet with parchment paper or silicone baking mat.

In a large bowl, using a hand-held mixer or stand mixer with paddle attachment, cream the butter and sugars together on medium speed, about 3 minutes. Mix in the peanut butter, egg, and vanilla (in that order). Scrape down the sides of the bowl as needed. Slowly mix in the baking soda and flour. Do not overmix. Fold in the quick oats, M&Ms, and chocolate chips. If the dough is very soft and unmanageable by hand, chill the dough for 30 minutes before rolling.

Rolls balls of dough, about 2 Tablespoons of dough per ball, onto prepared baking sheet. Press a few extra M&Ms on top for looks, if preferred. Bake for 9-10 minutes - do not bake past 10 minutes. The cookies will appear undone. I too mine out at 9 minutes, which is recommended. Slightly press down the baked cookies with the back of a spoon, since the cookies only slightly spread in the oven. Allow cookies to cool on baking sheet for 10 minutes before transferring to a wire rack. Cookies will firm up as they cool. Store cookies covered at room temperature for up to 1 week.

Baked cookies freeze well for up to 3 months. Unbaked cookie dough balls freeze well for up to 3 months too. Bake frozen cookie dough balls for an extra minute, no need to thaw. Click here for my tips and tricks on freezing cookie dough.

Recipe Notes:

*You may use unsalted butter in this recipe. If so, add 1/4 tsp salt with the flour.

*Please use quick oats in this recipe. You need the slightly finer texture from the quick oats in order to give the cookies a more uniform texture. Quick oats will act more as a binder in this recipe than whole oats would, since the consistency is more powdery and the oats are smaller in size.

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  1. I made these this evening for a bake sale. I added 1/4 cup of each M&M to make 3/4 cup ( plain, peanut butter & peanut) I baked them for 9 minutes, cooled on pan for 10. Just came out dry & bland. Will try again another time.

  2. First off, you are my go to place for recipes. I love that you give the weight measurements for ingredients & I know when I make one of your recipes, it will be delicious. I did have a question about this recipe. The cookies tasted great, but when I cooked them, they were still in the same ball shape. The next batch, I flattened before cooking & the looked exactly the same when I finished cooking them. No spread at all. They were really good still & I want to make they again. Do you have any advice on where I may have went wrong? Thank you!!

    • Hi Tiffany! No worries here, all I would do is reduce the flour the next time you make these. Sometimes cookies spread too much, sometimes they don’t spread at all. My solution is always the flour. I would reduce down to 1 cup when you make them again.

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