Preheat the oven to 350°F. Grease a 9-by-13-inch baking pan or line it with parchment paper.
In a large bowl, beat 1 cup unsalted butter, 1 cup packed light brown sugar, and ½ cup granulated sugar until smooth and creamy.
Beat in 2 large eggs, one at a time, then mix in 2 teaspoons vanilla extract.
In a separate bowl, whisk together 1 ½ cups all-purpose flour, 2 cups old-fashioned rolled oats, ½ teaspoon kosher salt, 1 teaspoon baking soda, and 1 teaspoon baking powder.
Add the dry ingredients to the wet ingredients and stir just until combined.
Fold in 2 cups semisweet chocolate chips.
Transfer the dough to the prepared pan and press it into an even layer.
Bake until the top is golden brown and the center is set, 25 to 30 minutes.
Let cool completely in the pan before slicing into bars.
