Preheat the oven to 325 degrees F (165 degrees C).
In a large bowl, cream together butter, brown sugar, and white sugar until fluffy. Beat in eggs one at a time, then stir in the vanilla. Combine the flour, baking soda, salt, and cinnamon; stir into the creamed mixture. Mix in oats and nuts until just blended. Drop by heaping teaspoonfuls onto ungreased cookie sheets. Cookies should be at least 2 inches apart.
Bake for about 12 minutes in the preheated oven. Cool cookies on a wire rack.