Preheat oven to 350°F. Line two large baking sheets with baking trays and set aside.
In a medium-sized mixing bowl, whisk together the flour, cinnamon, baking soda, and salt. Set aside.
In a separate large mixing bowl using an electric mixer, cream together the butter, brown sugar, and granulated sugar for about 1-2 minutes or until well combined. Mix in the egg and vanilla extract, stopping to scrape down the sides of the bowl as needed. Slowly add the dry ingredients to the wet ingredients and mix on low speed until just combined. Mix in the oats, then the chocolate chips until just combined. Cover tightly and refrigerate for at least 30 minutes.
Using a 1.5-2 tablespoon cookie scoop, scoop the dough onto the prepared baking sheets, making sure to leave a little room between each one. Bake in separate batches (keep the other batch of cookie dough in the refrigerator while the first batch bakes) at 350°F for 10-13 minutes or until the tops of the cookies are set.
Remove from the oven and cool on the baking sheet for 5-10 minutes, then transfer to a wire rack to cool completely.