My Dad's Mom, Grandma Johnson, was the best cook and baker. Everything she made was delicious. A lot of what I learned about cooking and baking came from Grandma Johnson through my mother (Grandma taught my Mom how to cook).
In a medium bowl, whisk flour, baking powder, baking soda, and salt; set aside.
Cream butter and sugar together; add egg and vanilla until well combined. Mix in flour mixture. Gently fold in oatmeal, coconut and nuts (if using).
Drop by teaspoonful onto greased cookie sheet. Bake for approximately 12 minutes or until cookies are lightly golden brown. For chewier cookies, bake for less time and for crunchier cookies, bake for more time. Cool on wire rack.