Heat the oven to 350 degrees Fahrenheit and cover two baking sheets with parchment paper. The lined pans should be ready before the dough is mixed so the cookies can go straight into the oven.

Beat the room temperature butter with the brown sugar in a large bowl until the mixture looks smooth, then blend in the eggs one at a time and add the vanilla. The finished mixture should be creamy and uniform, with no visible streaks of butter.

Add the flour, baking soda, baking powder, and salt to the bowl, mixing only until the dry ingredients disappear; fold in the oats until they are distributed throughout the dough. Stop as soon as the dough comes together so the cookies stay tender rather than heavy.

Pour the powdered sugar into a small bowl for coating the dough. Use a bowl wide enough to turn each portion without pressing or warming the dough.

Scoop portions of about 1 ½ tablespoons, roll each mound in the powdered sugar, and arrange eight portions on each prepared baking sheet. The dough should have generous space around it because the butter-rich cookies spread as they bake.

Bake the trays at 350 degrees Fahrenheit for 12 to 14 minutes. Look for a golden brown perimeter and set edges while the centers remain slightly soft beneath their cracked tops.

Leave the cookies on the baking sheets until fully cool, then transfer them to an airtight container. Once cool, the edges should offer light crisp resistance while the centers stay softer.