Preheat the oven to 350 degrees Fahrenheit. Line rimmed baking sheets with parchment paper and set aside. In a medium bowl whisk together the flour, baking soda, cinnamon, and salt until completely mixed.
2 cups all purpose flour, 1 teaspoon baking soda, 1 teaspoon cinnamon, 1/2 teaspoon salt
In a large bowl, with a hand mixer or using a stand mixer fitted with the paddle attachment, beat together the butter, brown sugar, and granulated sugar until the mixture is light and fluffy. This will take between 3 and 6 minutes.
14 tablespoons unsalted butter, 3/4 cup granulated sugar, 3/4 cup light brown sugar
Add the eggs one at a time. Then add in the vanilla. Be sure to scrape down the edges of the bowl with a spatula before each addition.
2 large eggs, 1 teaspoon pure vanilla extract
Add in the flour mixture. With the mixer on its lowest setting, beat the flour mixture into the wet ingredients until it just begins to combine. Then turn the mixture up and finish combining it until it is just combined. Be careful not to continue mixing after the flour is combined in.
Mix in the oats.
2 cups old fashioned oats
Using a 1 1/2 tablespoon cookie scoop, scoop the cookies and roll them into balls. Place 2 1/2 inches apart on a baking sheet. Bake for 11 to 12 minutes or until the edges of the cookies begin to turn golden brown. For best results, rotate the pan halfway through. Remove from the oven, let cool on the baking sheet for 2 minutes, and then transfer to a cooling rack to cool completely. Enjoy right away or store in an airtight container for up to 1 week.