Preheat the oven to 300 degrees F (150 degrees C). Grease cookie sheets. Stir together the flour, baking soda, salt and oats; set aside.
In a medium bowl, cream together the butter and brown sugar until smooth. Beat in the eggs one at a time then stir in the vanilla. Mix in the dry ingredients until well blended before stirring in the chocolate chips. Drop by heaping spoonfuls onto the prepared cookie sheet at least 3 inches apart. Flatten cookies to 1/2 inch thick.
Bake for 21 minutes in the preheated oven, until lightly browned. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.