Preheat the oven to 350℉. Grease a 9X9-inch baking pan with non-stick cooking spray or butter or line with parchment paper.
In a large bowl, stir together the melted butter, sugar, brown sugar, egg, and vanilla until fully incorporated. Add the flour, oats, baking powder, and salt and stir just until no streaks of flour remain. Fold in the chocolate chips.
Spread the batter into the prepared baking pan, spreading it well into the corners of the pan and smoothing the top as best as you can. Bake in the preheated oven for 25-30 minutes or until lightly golden. Let cool at least slightly before serving. Serve as is or with ice cream or whipped cream. Enjoy!
Notes
Or use unsalted butter with an additional ¼ teaspoon of salt added to the recipe.
Milk chocolate, dark chocolate, or chopped/chunks would be great instead, if preferred.