Heat 2 tablespoons of olive oil in a skillet over medium heat. Add the chopped onion and green pepper and cook for 3 to 5 minutes until the onions are translucent. Add the garlic and cook for 1 minute longer.
Add the crushed tomatoes, tomato sauce, 1 1/2 teaspoons of salt, 1/4 teaspoon of pepper, oregano, and 1/4 cup of Parmesan cheese. Bring the sauce to a simmer; reduce the heat to low and continue cooking for 20 minutes.
For the Meatballs and Serving
Soften the bread crumbs in the milk in a large bowl. Add the ground beef and seasoned salt.
Shape the meat mixture into 1-inch meatballs.
Heat 2 tablespoons of olive oil in a large skillet over medium heat and brown the meatballs, turning frequently to brown all sides.
Transfer the meatballs to the simmering sauce and let them cook for 5 to 10 minutes, or until they reach 160 F (165 F if you happen to be using ground poultry).
Meanwhile, cook the spaghetti in boiling salted water following the package directions.
Drain the spaghetti and serve with the meatballs, sauce, and Parmesan cheese.