In a large mixing bowl, whisk together the eggs, vanilla and brown sugar. Add the baking powder, cinnamon, salt and both types of oats. (Note: If you want to use all of one type of oat, that's totally fine! I just like to mix mine up with this recipe and when making granolas!) Pour in the milk and oil and whisk well. Batter will be slightly 'loose.' Pour into the prepared baking dish and bake for 30 minutes, or until toothpick comes out clean in the middle.