In a large bowl, dissolve yeast and sugar in water, let stand for 5 minutes. Add oil and salt. Stir in flour, a cup at a time, to form soft dough. Turn onto floured board, knead until smooth and elastic for about 2-3 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled in size (about 45 minutes).
Meanwhile, brown the beef and onion and drain. Punch dough down, divide in half. Press each into a greased 12" pizza pan. Combine the tomato sauce, oregano and basil and spred over each crust. Top with the beef mixture, green pepper and cheese. Bake at 400 degrees for 25-30 minutes or until the pizza crust is lightly browned.