Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, cream together the butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add this to the creamed mixture, mixing until just combined.
Stir in the oats, chocolate chips, and pecans until evenly distributed.
Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.
Bake for 10-12 minutes, or until the edges are golden brown. Allow the cookies to cool on the baking sheets for a few minutes before transferring them to wire racks to cool completely.

Variations & Tips
For a different twist, you can substitute walnuts for pecans or add a handful of dried cranberries for a touch of tartness. If you prefer a spicier cookie, try adding a teaspoon of cinnamon to the dry ingredients. For a chewier texture, reduce the baking time slightly and let the cookies cool on the baking sheet. These cookies also freeze well, so you can make a double batch and save some for later.