Preheat oven to 375°F (190°C). Line baking sheet with parchment paper.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy. Beat in the egg and vanilla extract until combined.
In a medium bowl, whisk together the flour, baking soda, cinnamon, and salt. Add to the creamed mixture and stir until just combined.
Stir in the oats, apples, and walnuts (if using).
Drop the cookie dough by heaping tablespoons onto the prepared baking sheet. Bake for 10-12 minutes, or until lightly golden brown. Allow to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
Interesting Facts
Oatmeal cookies are a classic American dessert.
Apples are a great source of dietary fiber and vitamins, and they add a delicious flavor to these cookies.
Walnuts add a nice crunch and nutty flavor to the cookies, but can be omitted if desired.