Preheat oven to 400 degrees; grease 2 baking sheets. In a medium bowl, combine the flour, baking powder, and salt. Set aside. In a large bowl, beat together the butter and sugar on medium speed until light and fluffy. Beat in the egg. Gradually beat in flour mixture, 1/2 cup at a time, until well blended. Add oats and zest. Stir in raisins. If necessary add a SMALL splash of milk. Drop dough by rounded teaspoonfuls onto prepared baking sheets, spacing them 2 inches apart. Flatten slightly. Bake until golden, about 10 minutes. Remove from oven and cool for 1 minute. Transfer cookies to a wire rack to cool.