The night before, mix raisins and bourbon in a small bowl. Cover and let soak overnight.
Preheat oven to 375°.
Cream together butter and sugars in a large bowl. Beat in eggs, vanilla, and liquid from the bourbon-soaked raisins.
Add flour, baking powder, baking soda, and salt and mix just until combined. Fold in oats and raisins.
Cover with plastic wrap and chill for at least 1 hour or overnight.
Scoop dough in 1" balls onto a parchment-lined baking sheet.
Bake at 375° for 8-10 minutes, until edges are golden brown. Remove from the oven and let cool on the baking sheet.