Preheat oven to 375°.
Using an electric mixer, beat butter until smooth. Add brown sugar and granulated sugar, beating until smooth. Add eggs, one at a time, mixing just until incorporated. Beat in vanilla.
In a separate bowl, combine flour, oats, dates, baking soda, salt, and cinnamon. Add flour mixture gradually to butter mixture, mixing just until combined. Stir in nuts.
Drop dough by tablespoonful onto ungreased baking sheets. Bake 12-14 minutes, until golden brown. Transfer cookies to wire racks to cool.
Makes 5 dozen cookies.