Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper or silicone baking mats.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy. This usually takes about 2-3 minutes with a stand mixer.
Beat in the eggs one at a time, then stir in the vanilla extract until well combined.
In a separate medium bowl, whisk together the all-purpose flour, baking soda, salt, and cinnamon. This ensures the leavening agents and spice are evenly distributed.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Stir in the rolled oats, chocolate chips, and chopped pecans (if using) by hand until evenly distributed throughout the dough.
Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between cookies to allow for spreading.
Bake for 9-12 minutes, or until the edges are golden brown and the centers are still slightly soft. They will continue to set as they cool.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.