Soften yeast in the warm water in a large bowl.
Add warm milk, sugar, salt, margarine, and 2 cups flour; beat with hand rotary or electric beater until smooth, about 1 minute.
Add 1 cup flour and beat vigorously with a wooden spoon (150 strokes).
Add enough of the remaining flour to make a soft dough.
Turn onto a lightly floured surface and knead until smooth and elastic.
Cover with plastic wrap, then a towel, and let rest 20 minutes.
Punch down dough and divide into halves.
Shape into loaves.
Place, seam side down, in 2 greased 8x4x2-inch loaf pans.
Brush with oil, then cover loaves loosely with oiled waxed paper and plastic wrap.
(Be sure these layers are not tucked under the pans, as they must be loose enough to allow dough to rise.) Refrigerate 2 to 24 hours.
When ready to bake, remove from refrigerator, uncover, and let stand at room temperature 10 minutes.
Prick any gas bubbles with an oiled wooden pick or metal skewer.
Bake at 400°F 30 to 40 minutes.
Remove from pans, brush loaves with melted butter or margarine.
Cool on wire racks.