Preheat the Oven Preheat your oven to 350°F (175°C).
Cream the Butter and Sugars In a large bowl, beat the softened butter, granulated sugar, and brown sugar until creamy. Add the egg and vanilla extract and mix well.
Mix the Dry Ingredients In another bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the wet mixture.
Add Oats and Raisins Stir in the oats and raisins until evenly mixed.
Drop the Dough Drop rounded tablespoons of dough onto ungreased baking sheets, leaving space between each cookie.
Bake Bake for 10-12 minutes, or until the edges are golden brown. Allow to cool on the baking sheets for a few minutes before transferring to wire racks to cool completely.