Place milk, vanilla, butter, eggs, and brown sugar in a mixing bowl andf stir well.
Add oatmeal, salt, and baking powder and stir again.
Pour into greased baking dish. I use a 7x11 inch pan. You may ue any 2 quart baking dish.
Bake at 400° for 20 minutes or until the oatmeal is golden brown around the edges, and a toothpick inserted comes out mostly clean.
Notes
You may use quick oats if you prefer. The baked oatmeal will have a more cake-like texture with quick oats, while using old-fashioned oats makes it more crumbly. You may substitute white sugar or other sweetener. If you use white sugar or honey, decrease amount to 1/2 cup. Mix in some extras for added flavor: Chopped nuts, chocolate chips, raisins or chopped dates are delicious. I add about 3/4 cup of nuts or other add-in.