In a large bowl, whisk together the flour, cinnamon, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using an electric mixer, cream together the butter, brown sugar, and granulated sugar for 1-2 minutes until well combined. Add the egg and vanilla extract and mix until fully combined.
Slowly mix in the flour mixture and continue mixing until just combined, then mix in the oats and raisins until fully combined, making sure to scrape down the sides of the bowl as needed.
Cover the cookie dough tightly with plastic wrap and refrigerate for 30 minutes.
Meanwhile, preheat the oven to 350°F. Line two large baking sheets with parchment paper or silicone baking mats and set aside.
Once the dough is chilled, remove it from the refrigerator. Using a 1.5-2 tablespoon cookie scoop, scoop the cookie dough and drop onto the prepared baking sheets. Roll the cookie dough into balls and very gently press down with your hand to flatten each ball of cookie dough slightly (make sure not to flatten them completely, just slightly). Make sure to leave a little room between each ball of cookie dough as they will spread a little while they bake.
Bake in separate batches at 350°F for 10-12 minutes or until the edges of the cookies are lightly golden brown and the top is set. Remove from the oven and cool on the baking sheet for 5 minutes, then transfer the cookies to a wire rack to finish cooling.