Line two large baking sheets with parchment paper. Set aside.
Using an electric mixer, cream the butter, brown sugar, and granulated sugar on low to medium speed until light and fluffy, about 3 minutes.
1 cup unsalted butter, 1 cup light brown sugar, 1 cup granulated sugar
Add the eggs and vanilla extract, and mix until fully incorporated. Scrape down sides of the bowl as needed.
2 large eggs, 2 teaspoon(s) pure vanilla extract
Pour in the flour, both varieties of oats, cinnamon, baking soda, and salt. Mix on low speed just until combined.
2 ¼ cups all-purpose flour, 2 cups old-fashioned rolled oats, 1 cup quick oats, 2 teaspoon(s) cinnamon, 1 teaspoon(s) baking soda, ½ teaspoon(s) salt
Use a 2 tablespoon sized cookie scoop and scoop the dough onto the baking sheets. Space the dough about 2 to 3 inches apart.
Transfer the baking sheets to the refrigerator to chill for at least 30 minutes, longer if possible. While the dough is in the refrigerator, preheat the oven to 350°F.
Bake the cookies for 13 to 15 minutes. They’re done when the edges are brown, and the centers appear just barely underdone.
Remove the cookies from the oven and allow them to cool for 5 minutes before transferring to a cooling rack. They’ll finish setting while they’re on the hot baking sheet.
Enjoy! See post for tips and storage options.