Preheat the oven to 375°F and line baking sheets with parchment paper.
In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar together until light and fluffy, about 2–3 minutes.
Add the egg, vanilla extract, and maple syrup. Mix until completely combined.
In a separate bowl, whisk together the flour, baking soda, kosher salt, and cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing just until combined.
Add the quick-cooking oats and mix until evenly incorporated throughout the cookie dough. Avoid overmixing.
Scoop the cookie dough into approximately 1 1/2-tablespoon portions and place them a few inches apart on the prepared baking sheets.
Place the prepared baking sheets in the refrigerator and chill the scooped cookie dough for 20 minutes.
Transfer the chilled cookie dough directly to the preheated oven and bake for 9–11 minutes, or until the edges are set and lightly golden but the centers still look soft.
Allow the cookies to cool on the baking sheets for 5–10 minutes before transferring them to a wire rack to cool completely.