In a medium bowl, whisk together flour, cinnamon, salt, and baking soda; set aside.

In a large bowl, whisk together melted butter, brown sugar, maple syrup, and vanilla. Let butter cool for 1 minute, then whisk in egg. Add dry ingredients to bowl and stir until combined. Stir in oats.

Press plastic wrap over dough in bowl and let chill in refrigerator for at least 3 hours or overnight

Place oven racks in upper and lower thirds of oven. Preheat oven to 350°F. Line 2 baking sheets with parchment paper. Drop dough by rounded tablespoon onto prepared baking sheet.

Bake until golden, about 16 minutes. Let cool on sheet for 5 minutes then transfer to a wire rack to finish cooling. Cookies can be stored in a sealed container at room temperature for up to a week.