Use an electric mixer to cream together the butter, brown sugar and salt until light and fluffy, about 2 minutes.
Add the egg and vanilla, then beat on medium speed until fully incorporated, about 1 minute.
Add the flour and baking soda and mix until just barely combined.
Add the oats and mix for a few seconds, then add the chocolate chips and mix until fully combined.
Preheat the oven to 350 degrees, then mix together the granulated sugar and cinnamon in a small bowl.
Scoop rounded tablespoons of dough onto parchment lined baking sheets about 2 inches apart.
Use your thumb to gently press down on the middle of each ball of dough to create a small divot, then sprinkle each with cinnamon sugar.
Bake for 10-12 minutes. Less time will give you a chewier cookie and more time will result in a crispier cookie. Ovens vary, so be sure to keep an eye on them.
Allow cookies to cool right on the baking sheet, then serve while they're still warm.