Preheat oven to 375°F (190°C).
In a medium bowl, cream together butter, white sugar, and brown sugar.
Beat in eggs one at a time, then stir in vanilla.
Combine flour, baking soda, salt, and cinnamon; stir into the creamed mixture.
Mix in oats. Cover, and chill dough for at least one hour.
Roll the dough into walnut-sized balls, and place 2 inches apart on cookie sheets.
Flatten each ball slightly with a fork.
Bake for 8 to 10 minutes in preheated oven. Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.