In a food processor, pulse the rolled oats until they reach a coarse, flour-like texture, about 20 seconds. Set aside.
In a medium bowl, whisk together the oat flour, all-purpose flour, baking soda, and salt until well combined.
In a large bowl, use a hand mixer or stand mixer to cream the softened butter, light brown sugar, and granulated sugar together until light and fluffy, about 2-3 minutes.
Add the vanilla extract and milk to the butter and sugar mixture and mix until combined.
Gradually add the flour mixture to the wet ingredients, mixing on low speed until just combined and a dough forms.
Fold in the mini semi-sweet chocolate chips evenly throughout the dough.
Serve immediately or refrigerate in an airtight container for up to 5 days. Enjoy chilled or at room temperature.