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.
Mix in vanilla extract.
Whisk together flour, baking soda, cinnamon, and salt.
Gradually add the dry ingredients to the wet ingredients.
Fold in the rolled oats.
Stir in raisins or chocolate chips if using.
Scoop tablespoon-sized portions onto the prepared baking sheets.
Bake for 10–12 minutes until the edges are lightly golden.
Let cookies cool on the baking sheet for 5 minutes.
Transfer to a wire rack to cool completely.
