Preheat your oven to 350°F (175°C). This ensures that your cookies will bake evenly right from the start.
In a large mixing bowl, beat the room temperature unsalted butter and brown sugar together until the mixture is light and fluffy. This should take about 2-3 minutes.
Crack in the egg and pour in the vanilla extract. Mix until well combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.
Fold in the old-fashioned oats until evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto a parchment-lined cookie sheet, leaving enough space between each to allow for spreading. Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Enjoy your Easy Oatmeal Cookies warm or at room temperature!
