Measure 2.5 cups of oats and blend/pulse in a blender or a food processor until the oat is finely ground into a powder.
Add flour, baking powder, baking soda, and salt and pulse, set aside until ready to use.
Cream the butter in a large mixing bowl with an electric mixer or stand mixer for about 1 minute until creamy.
Add granulated and brown sugars and cream until fluffy (about 5 minutes), scrape down sides as needed.
Combine oil, water, and baking powder in a small bowl, add to the butter mixture, add vanilla extract and cream until blended.
Add half of the flour and oats mixture and mix, add the rest and mix.
Scrape down the sides, add the chocolate chips, grated chocolate, and raisins (if using), and mix on low speed.
Cover the bowl with plastic wrap and refrigerate for at least 30-60 minutes (or longer).
While the cookie dough chills, preheat oven at 375 °F and line 3 cookie sheets with parchment paper or silicon liners.
Scoop about 2 tablespoons of dough, roll into a ball, and place about 2 inches apart on a cookie sheet.
Bake for about 14-15 minutes until golden brown, take the cookie sheet out of the oven and allow the cookies to cool slightly for 5-10 minutes, then transfer to a wired rack to cool completely.
Makes about 36 3-inch cookies.