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Gluten Free Monster Cookies are the ultimate cookie mash-up of peanut butter, oatmeal, chocolate chips and M&Ms. They’re soft, chewy and bake up beautifully every single time.

overhead view of monster cookies made with peanut butter, oatmeal, chocolate chips and M&Ms candies

The Best Type of Oats for Monster Cookies

The kind of oats you select for this recipe are important because not all oats are created equal.

Use quick cooking oats if you want a lighter, softer cookie.

Use old fashioned oats if you prefer heartier, chewier cookies.

Image of dry oats. Quick cooking oats are pictured on the right and old fashioned oats on the left.

Different Types of Oats

The most commonly found oats at the grocery store are instant, quick cooking, old fashioned and steel cut. They’re all oats, but they are processed differently.

Instant, quick cooking and old fashioned oats are made by steaming whole oat groats (the grains) to soften them, and then they’re rolled into flat flakes. That’s where you get the term “rolled oats”.

Instant oats are rolled super thin so that they absorb moisture quickly and cook up in an instant.

Quick oats are not quite as thin as instant, but are still pretty thin. They take a minute or two more to cook, and have more texture in comparison.

Old fashioned are the thickest of the three and take longer to cook. They also retain a lot more texture and are heartier after they’re cooked.

Steel cut oats, on the other hand, are not steamed or rolled like old-fashioned or quick-cooking oats. Whole oat groats are chopped into smaller pieces using steel blades. This minimal processing retains more of the oat’s natural texture and nutritional content and they also take longer to cook.

The different types of oats will yield different results in the final cookies because of how quickly they absorb water and the time they take to cook.

Quick cooking and old fashioned both gave great results depending on your preference for a softer cookie versus a chewier cookie. I prefer the softer, lighter quick oats version. My husband Ryan prefers the old fashioned. It’s a house divided.

Instant and steel cut, though, are not recommended and will not perform well with this recipe.

overhead view of monster cookie dough in a mixing bowl — Monster Cookie dough prepared with quick cooking rolled oats

What Makes this Recipe Gluten Free?

This monster cookie recipe is flourless. There is no need for any substitutions as long as your oats are certified gluten free. Bob’s Red Mill and many of the organic generic store-brand oats are gluten free. Always check your labels, though.

Overhead view of monster cookies cooling on a rack

What Kind of Peanut Butter is in Monster Cookies?

Conventional creamy peanut butter like the popular brands Jif or Skippy is best for this recipe.

I did test out a batch using natural peanut butter. The recipe still essentially works, but the final cookies were a little more crumbly.

How to Get Round Monster Cookies

I like to use a 4” round cookie cutter and run it in a circular motion around the baked cookies when they’re fresh out of the oven. You’ll see this in the photos below.

The cookies are still pliable when they come out of the oven, so rounding them with the cookie cutter helps to shore up the edges and make them more uniformly round. It also makes them a little thicker since they spread a bit while they bake.

This isn’t a required step and more organic shaped cookies are 100% acceptable!

uncooked monster cookie dough balls on a sheet tray before baking — pre-bake

monster cookies after they've been baked — pre-bake