In the mixing bowl of an electric mixer, stir together 1/2 cup warm water, 1 tablespoon sugar, 1/4 cup bread flour, and yeast. Let grow for about 5 minutes. It will bubble almost immediately.
Measure oats, 4 1/2 cups warm water, whole wheat flour, salt, 2/3 cup sugar, and 2/3 cup oil into the mixing bowl. Mix on low speed with a dough hook for 1 to 2 minutes. Increase speed slightly, and begin adding bread flour 1/2 to 1 cup at a time until dough pulls away from sides of bowl. Humidity determines how much flour you need before the bread pulls away from the edge of the bowl. It is normal for the dough to be sticky.
Place dough in an oiled bowl, and turn to coat the surface. Cover with a damp cloth. Let rise in a warm spot for 1 hour, or until doubled in size.
Divide dough into 6 pieces. Shape loaves, and place in greased 8 x 4 inch pans. Let rise until dough is 1 inch above rim of pans, usually 1 hour.
Bake at 350 degrees F ( 175 degrees C) for 35 minutes, or until tops are browned. Let cool in pans for 10 minutes, and then turn out onto wire racks to cool completely.