In a medium bowl, cream together butter, white sugar, and brown sugar. Beat in eggs one at a time, then STIR (do not beat in) in vanilla. Combine flour, baking soad, salt, and cinnamon in another bowl. Wisk it together; stir into the creamed mixture. Mix in oats ONE cup at a time. Cover and chill dough for at least one hour.
Preheat the oven to 375 degrees. Grease cookie sheets. Pinch the dough into walnut size balls, and place 2 inches apart on cookie sheets.
Bake for 8 to 10 minutes(i perfer 8min with my oven). Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.