Combine water, yeast and sugar in a large mixer bowl. Let stand 5 minutes, until foamy. Add salt, oil and 1 cup flour; beat for 2 minutes at medium speed. Add enough remaining flour to make a soft dough.
Knead dough on lightly floured surface for 6 to 8 minutes, until smooth and elastic. Place dough in a well greased bowl, turning once to coat. Cover and let rise in a warm, draft-free place until doubled, about 1 hour.
While dough is rising, cook bacon in large skillet until just browned but not crispy. Drain well and crumble or chop into small pieces. Reserve 2 tablespoons bacon drippings in skillet. Add onion and cook over medium heat for 15 to 20 minutes or until onions are lightly caramelized. Add Port wine and cook until very little liquid remains. Set aside to cool.
Punch dough down. Roll into a 15 x 10-inch rectangle on parchment paper. Spread onions over dough and then sprinkle with bacon and cheese. Roll dough up from long side, jelly roll style. Pinch seams to seal. Transfer loaf (and parchment paper) to baking sheet.
Cover and let rise in a warm, draft-free place until nearly doubled, about 30 to 45 minutes. Slash top with cuts about 2-inches apart and 1/4-inch deep, using a very sharp knife.
Bake in preheated 375°F oven for 25 to 30 minutes, until golden. Remove to wire rack to cool.