In a large bowl, use an electric mixer to cream together the butter, brown sugar and granulated sugar until light and fluffy.
Add the eggs, one at a time, mixing until well combined. Mix in the vanilla extract and milk.
Gradually add the oats; mix until well incorporated.
In a separate bowl, whisk together flour, baking soda and salt.
Gradually add the flour mixture to the oat mixture. Stir in the chocolate chips.
Cover and the bowl and refrigerate the dough for at least 1-2 hours, or up to 2 days.
If the dough is too firm to scoop when you take it out of the fridge, leave it on the counter to sit at room temperature until it softens slightly.
Preheat oven to 350° F. Line baking sheets with parchment paper or silicone baking mats.
Using a 4-teaspoon spring-loaded scoop, drop dough onto prepared pans. Place the cookie dough about 2 inches apart.
Bake until cookies are lightly browned on the edges, but still soft in the center (about 10-12 minutes). Let cool on pans for 5 minutes. Remove from pans and let cool completely on wire racks.