Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a mixing bowl, whisk together the flour, baking soda, salt, and cinnamon. Set aside.
In a separate large bowl, beat the softened butter, brown sugar, and granulated sugar together until creamy and smooth.
Add the egg and vanilla extract to the butter mixture, mixing until well combined.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined.
Fold in the rolled oats, chocolate candies, and nuts (if using) until evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden.
Remove from the oven and let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
For an added festive touch, you can drizzle melted white chocolate over the cookies once they cool.