Combine the oats, margarine, molasses, and salt in a large bowl. Add the boiling water and mix well. Let stand for 1 hour.
Dissolve the yeast in the ½ cup warm water; when bubbly, add to the oat mixture. Work in the flour to make a thick dough. Knead well and continue to add flour until the dough is shiny and no longer sticky.
Place in a greased bowl, cover, and set in a warm place to rise until doubled, about 1-½ hours.
Divide in half, shape into two loaves, and put into two greased 8-inch by 4-inch loaf pans. Let rise again until well shaped and doubled. Preheat the oven to 350 degrees F.
Bake for 1 hour. Let cool on wire racks for 10 minutes, then turn out of the pans to cool completely. When cool, wrap and store. This bread freezes very well.