Preheat your oven to 350°F (175°C).
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until smooth.
Beat in the eggs one at a time, followed by the vanilla extract.
In a separate bowl, combine the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Fold in the oats, chocolate chips, and chopped nuts.
Drop rounded tablespoons of dough onto ungreased baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 12-15 minutes, or until golden brown.
Allow the cookies to cool on the baking sheets for a few minutes before transferring them to wire racks.
Enjoy your freshly baked cowboy cookies with a glass of milk!