If adding raisins, plump the raisins in hot water. Drain before stirring into the batter.
Cream butter, sugar and brown sugar together.
Beat in eggs one at a time, then stir in vanilla.
Sift dry ingredients together and add to creamed mixture.
Stir in oats and drained raisins, if desired.
Cover, and chill dough for at least 1 hour.
Preheat the oven to 375 degrees F. Drop walnut sized spoonfuls of dough onto baking sheet and placing 2 inches apart.
Bake for 8-10 minutes in preheated oven.
Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.