Melt the butter in a medium saucepan over low heat, stirring until completely liquid. Allow to cool slightly for 10 minutes.

Mix the cooled melted butter with brown sugar and granulated sugar in a large mixing bowl until smooth and creamy.

Incorporate the eggs, one at a time, and then add vanilla extract until well combined.

Combine dry ingredients: whisk flour, oats, baking soda, salt, and cinnamon in a separate bowl.

Gradually add dry ingredients to wet mixture, stirring gently until just combined.

Fold in chocolate chips and nuts if using.

Chill the dough covered with plastic wrap in the refrigerator for at least 1 hour.

Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

Scoop 3 tablespoons of dough onto each baking sheet, spacing 2 inches apart.

Bake for 12-15 minutes or until edges are golden brown.

Cool on sheets for 5 minutes before transferring to wire racks.