Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, combine the rolled oats, all-purpose flour, brown sugar, granulated sugar, baking powder, baking soda, and salt. Mix well.

In a separate bowl, cream the softened butter until smooth. Add the egg and vanilla extract, mixing until well combined.

Gradually add the wet ingredients to the dry ingredients, stirring until just combined. If desired, fold in the raisins or chocolate chips.

Using a tablespoon or cookie scoop, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 12-15 minutes, or until the edges are lightly golden.

Remove from the oven and let the biscuits cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.