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.
Preheat the oven to 375 degrees F (190 degrees C). Grease cookie sheets. Roll the dough into walnut sized balls, and place 2 inches apart on cookie sheets. Flatten each cookie with a large fork dipped in sugar.
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.
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