In a large bowl, combine flour, baking soda, salt, and cinnamon.

Set aside the dry ingredients.

In a separate bowl, cream together butter, peanut butter, white sugar, and brown sugar using an electric mixer at medium speed until light and fluffy.

Add eggs one at a time, beating well after each addition.

Blend in vanilla and milk.

Gradually stir the dry ingredients into the creamed mixture, blending well.

Stir in oats and raisins (if using).

Drop by tablespoon onto well-greased baking sheets, leaving about 2 inches of space between each cookie.

Bake in a preheated 350°F (175°C) oven for 15 minutes, or until light golden brown.