Preheat the oven to 350F. Line a large baking sheet with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and brown sugar until light and fluffy.
4 tablespoons butter, 1 cup light brown sugar
Add the egg, peanut butter, and vanilla and mix to combine.
1 large egg, 1 cup creamy peanut butter, 1 teaspoon pure vanilla extract
Next add the oats, flour, and baking soda. Mix to combine again.
2 cups old fashioned oats, ½ cup all purpose flour, 1 teaspoon baking soda
Add the M&Ms and candy corn and fold them into the cookie dough with a rubber spatula.
½ cup halloween M&Ms, ¼ cup candy corn
Scoop 1” balls onto the prepared baking sheet, making sure to place them at least 2” apart.
Bake the cookies for 15 minutes, or just until the edges are set. Then, remove them from the pan and allow them to cool to room temperature on the pan. press the candy eyes on the cookies while they’re still warm.
Enjoy immediately. Store any leftover cookies in an airtight container at room temperature for up to five days.