Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Cream butter, brown sugar, and granulated sugar until light and fluffy.
Beat in eggs one at a time, then stir in vanilla.
Whisk flour, baking soda, salt, and cinnamon in a separate bowl.
Gradually add dry ingredients to wet mixture; mix until combined.
Stir in oats, dried cranberries, and nuts if using.
Drop rounded tablespoons of dough onto prepared baking sheets, spacing 2 inches apart.
Bake for 10–12 minutes, until edges are golden but centers are soft.
Cool 5 minutes on baking sheets before transferring to wire racks to cool completely.