Makes 5 dozen 

½ pound (2 sticks) unsalted butter, at room temperature
½ cup white sugar
1 cup light brown sugar
2 large eggs, at room temperature 
1 tablespoon vanilla extract 
1 tablespoon water
2 ½ cups old fashioned oats
1 ¾ cups all-purpose flour
1 teaspoon baking soda
½ teaspoon kosher salt

Preheat the oven to 375 degrees. Line a cookie sheet with parchment or wax paper.  

Put the butter and sugars in a large mixing bowl and using a spoon or rubber spatula, mix until smooth. Add the eggs, vanilla extract, and water and mix until just combined. Scrape down the sides of the bowl, add the oats and flour and then sprinkle in the baking soda and salt. Mix until everything is well incorporated. 

Put heaping tablespoons of dough on the prepared sheet and put in the oven. Bake until brown on the edges and soft in the middle, about 12 minutes. Cool on the cookie sheet and then transfer to a plate. Repeat with the remaining dough.