Preheat the oven to 350 degrees. Grease a 9 x 13 inch pan.
In the bowl of an electric mixer, beat together butter, light brown sugar, granulated sugar, vanilla, cinnamon, salt, and cider vinegar until smooth.
Add the eggs, beating after each addition, until the mixture is light and creamy.
Sprinkle the baking soda and flour on top of the mixture and beat until combined, about 1 minute.
Add the oats and chocolate chips or other additions, and stir to combine. Press the batter into the prepared pan.
Bake for 33-38 minutes, or until edges are set, color is golden brown, and centers no longer look wet.