Add all ingredients to a large bowl and mix until blended. Cover and let rest 20 minutes so the oats can absorb some of the liquid. After 20 minutes, knead for 10 minutes by hand.
Place the dough in a lightly greased bowl until it has notably risen. Gently deflate the dough and form into a log shape. Place into a greased pain de mie pan.
Cover with greased plastic wrap and let it rise again until it is 1" from the top, 60 to 90 minutes. Preheat the oven to 350 °F toward the end of the rise time.