In a large bowl combine flour, baking soda, baking powder and salt. Mix to combine and set aside.
In a mixing bowl or stand mixer, beat butter and sugars until light and creamy, approximately 2-3 minutes. Mix in eggs, one at a time, until well combined, but do not over mix. Mix in vanilla.
Pour flour mixture into butter and sugar mixture and stir to combine well. Add in oats and chocolate chips or raisins and stir until well combined, but do not over-mix.
Place cookie dough in refrigerator to chill for at least 30 minutes or up to 24 hours.
Once ready to bake, preheat oven to 350 degrees F.
Scoop cookie dough, approximately 2 tablespoons at a time, and place two inches apart on a cookie sheet that has been lined with a silicone baking mat or sprayed lightly with non-stick cooking spray.
Bake for approximately 11-13 minutes or until starting to turn golden brown.
Let cool on baking sheet for approximately ten minutes, then transfer to a wire rack for cooling. Repeat process with remaining cookie dough.
Store tightly covered and enjoy.