Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone mats.
In a large bowl, beat butter, brown sugar, and granulated sugar until light and fluffy (~2–3 mins). Add eggs, one at a time, beating well after each. Stir in vanilla extract.
In a separate bowl, whisk together flour, baking soda, salt, and cinnamon.
Gradually add dry ingredients to wet mixture, mixing on low speed or by hand until just combined. Don’t overmix!
Stir in oats, chopped pecans, and corn syrup until evenly distributed. The dough will be thick, sticky, and slightly glossy.
Use a cookie scoop or tablespoon to portion dough into rounded balls. Place 2 inches apart on prepared sheets. Optional: Press a few extra pecan pieces on top for bakery-style look.
Bake 10–12 minutes, until edges are golden brown and centers look set but still soft. Remove from oven — they’ll firm up as they cool.
Let cool on baking sheet 5 minutes, then transfer to wire rack.
