Preheat the oven to 375°F (190°C). In a large bowl, whisk the oat flour, tapioca starch, brown rice flour, xanthan gum, baking powder, and salt until even.

In a medium bowl, whisk the warm milk, sugar, and yeast. Let sit 5-10 minutes until foamy, then whisk in the oil, eggs, and vinegar until smooth.

Pour the wet mixture into the dry ingredients. Stir with a spatula for about 30 seconds, just until no dry flour remains.

Grease a 9x5 inch loaf pan. Scrape the batter in, smooth the top, cover loosely, and let rise in a warm spot for 45-60 minutes until domed an inch above the rim.

Uncover and bake 40-45 minutes, until deep golden brown and an instant-read thermometer reads 200-205°F (93-96°C) in the center.

Cool the loaf on a wire rack for at least 1 hour, then slice with a serrated knife.