More than just a chocolate chip cookie, Monster Cookie Bars are a delectable combination of oats, peanut butter, classic cookie flavor and of course candies. These cookies are chewy, crunchy and gooey, all the best cookie traits in one. A sweet treat for all cookie lovers.

cast iron pan filled with a chocolate chip and m and m cookie

Monster Cookie Recipe

I love to cook this Monster Cookie Bar recipe right in my cast iron pan. It makes the most crispy edge and you can slice the bars into triangles, squares or even rectangles. These can also be made in a 9×13 inch baking dish if you prefer.

Monster cookies are a family favorite around here, and for some reason, cookies in bar form are just so much better. They are also so much easier to make, you only have to make one big cookie, instead of a few batches.

cast iron pan filled with a cookie with chocolate chips and m and ms with a piece cut out

Monster Cookie Ingredients

This cookie recipes starts as a basic cookie, then takes it to a whole new delicious level with the addition of some simple ingredients. You will need the following to make this monster cookie recipe:

butter– unsalted and softened to room temperature
peanut butter– creamy peanut butter works best, not natural peanut butter for baking
sugar and brown sugar
vanilla
eggs
all purpose flour
salt
baking soda
mini chocolate chips– semi-sweet
Mini M&Ms
quick rolled oats

⭐️ Full ingredient measurements and recipe instructions can be found in the recipe card at the bottom of this post.

cast iron skillet chocolate chip cookie with colorful chocolate covered candies

How to make Monster Cookie Bars

First, to make this simple recipe for monster cookie bars, in a large mixing bowl, or stand mixer cream together the butter, peanut butter, sugar and brown sugar, vanilla and eggs.

Mix with an electric mixer for about one minute, until the sugars are well mixed in.

butter, sugars, eggs and vanilla mixed together in a large glass mixing bowl

Then, add in the flour, salt and baking soda and quick oats.

Mix in the dry ingredients with the mixer until well combined and a thick cookie batter has formed.

uncooked cookie dough in a large glass bowl

Lastly, fold in the mini chocolate chips and mini M&Ms until they are fully incorporated into the cookie dough. This can be done with the mixer, if your mixer can handle it, or mix in with a wooden spoon or clean hands.

uncooked chocolate chip cookie dough with colorful candies mixed in, pressed into a cast iron pan

Press the cookie dough into a 12 inch cast iron pan or 9×13 baking dish. Be sure to evenly press the cookie into the pan so that it will bake evenly.

Bake the cookie at 375º F for 18-20 minutes, until cooked through and crispy on the edges.

Remove from the oven and allow to cool slightly before slicing into bars.

chocolate chip cookie in a large cast iron pan with a piece cut out of the cookie

How to Store Monster Cookie Bars

Monster cookie bars can be left in the pan on the counter for up to 3 days, cover tightly with foil or plastic wrap to keep soft.

These can also be sliced and kept in an air tight container or cookie jar on the counter for up to 3 days.

Monster cookie bars can also be frozen for up to 3 months. Slice into bars and place into a freezer bag or air tight container and freeze.

chocolate chip cookie in a cast iron skillet with a piece cut out on a plate and topped with vanilla ice cream

Monster Cookie Bar Recipe

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Some of our other favorite cookie recipes to try:

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