In a large mixing bowl, beat together room temperature butter, brown sugar, and white sugar with a hand mixer.
Next, add in eggs and vanilla extract. Then, beat again.
Pour in the oat flour, salt, baking powder, and rolled oats. Mix wet and dry ingredients thoroughly. The batter will be thick.
Fold the chocolate chips into the batter with a rubber spatula. Then spread into a greased 9x13 baking dish.
Bake 25-30 minutes or until a toothpick inserted in the center comes out clean.
Let the blondies cool completely before adding frosting. Slice and enjoy!