In a large heavy pot, heat olive oil over medium heat. Add onion and peppers and Italian sausage. Cook 3-5 minutes. Add oregano and crushed garlic and cook about 2 more minutes. Add all canned tomatoes. Add 1/2 can water from each can. Be sure to stir well to get all the tomato out of the cans. Stir gently with wooden spoon. Add salt, pepper and basil. Reduce to simmer and cook for about 4 to 5 hours. Feel free to add more basil and garlic to taste. I like to prepare the sauce the day before I make the lasagna. Be sure to heat the sauce before assembling lasagna.