You can make your own oat flour with a food processor - it is a bit hard to get it as fine as store-bought, but it does work. Just pulse until very fine.
Preheat the oven to 350°.
In a large bowl, whisk together the milk, eggs, sugar, and salt.
In a separate bowl, whisk together the flour and baking powder.
Add the flour mixture to the milk mixture and stir until combined. It will be a batter consistency.
Line a loaf pan with parchment paper. (Rather essential, as the bread sticks terribly otherwise.) Pour in the batter.
Bake for 30-40 minutes, or until a toothpick inserted in the middle comes out clean.It may be a bit hard for it to brown because of the parchment paper. Allow to cool for about 10 minutes then place on a cooling rack to cool completely.
When it is cooled, place in a Ziploc bag and seal it. This is best served the 2nd day, so it's not so crumbly. But sealing it in a Ziploc bag really helps it retain its moisture.