In a skillet, combine oil, onion, bell pepper and garlic. Saute on stove top over medium heat until vegetalbes are tender (do not brown). Add tomatoes, oregano, salt and pepper, and bring to a boil for 1 minute. Reduce heat and simmer for 10 minutes. Add scallops and simmer another 3 minutes. Serve warm sauce over pasta. Top with grated Parmesan cheese (if desired).