In a bowl, dissolve yeast in warm water. Add oats, milk, shortening, 1/2 cup sugar, eggs, salt and 2 cups flour; beat until smooth. Add enough remaining flour to form a soft dough. Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and rise in a warm place until doubled, about 1 hour.
Punch dough down; cover and let rest for 10 minutes. Divide in half; roll each portion into a 16x8-in. rectangle. Brush with butter. Combine cinnamon and remaining sugar; sprinkle over dough to within 1/2 in. of edges. Roll up jelly-roll style, starting with a short side; pinch seams to seal.
Place loaves seam side down in two greased 9x5-in. loaf pans. Cover and let rise in a warm place until doubled, about 25 minutes. Bake at 375° for 40-45 minutes or until golden brown. Cover loosely with foil if bread browns too quickly. Remove from pans to cool on wire racks.