In a small bowl, dissolve yeast and sugar in warm water.
Let stand until creamy, about 10 minutes.
In a large bowl, combine the yeast mixture with the oil, margarine, salt and 1 1/2 cups flour; stir well to combine.
Mix in the remaining flour, 1/2 cup at a time, beating well after each addition. When the dough has pulled together, turn it out onto a lightly floured surface and knead until smooth and supple, about 8 minutes. Lightly oil a large bowl, place the dough in the bowl and turn to coat with oil. Cover with a damp cloth and let rise in a warm place until doubled in volume, about 1 hour.
Deflate the dough and turn it out onto a lightly floured surface and form into a loaf.
Place the loaf into a lightly greased 9x5 inch loaf pan. Cover with a damp cloth and let rise for 15 minutes. Meanwhile, preheat oven to 350 degrees F (175 degrees C).
Bake in preheated oven for about 30 minutes or until the top is golden brown and the bottom of the loaf sounds hollow when tapped. Cool in pan 5 minutes and then turn out onto rack and cool completely.
