Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
In a large bowl, cream the softened butter with brown and granulated sugars until light and fluffy.
Add eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the butter-sugar mixture, mixing until just combined.
Fold in the rolled oats until evenly distributed throughout the dough.
Stir in the semisweet chocolate chips and optional nuts, reserving a few chips to press on top.
Scoop dough by rounded tablespoon (or use a cookie scoop) onto prepared sheets, spacing about 2 inches apart.
Press a couple of reserved chocolate chips onto the top of each dough mound for a finished look.
Bake 9–12 minutes, until edges are set and centers look slightly soft for a chewy result.
Allow cookies to cool on the baking sheet 5 minutes, then transfer to a wire rack to cool completely.