Place tomatoes, onion, oregano and 1 teaspoon salt in blender just long enough to chop onion. Bring to a boil and allow to simmer.
Drain sausages on paper towels and add to simmering sauce.
Combine ground beef, bread crumbs, salt and pepper. Form mixture into balls and add to simmering sauce. Cover pan and continue cooking about 2 hours over low heat. Fifteen minutes before sauce is finished, add mushrooms and remove garlic. Serve over pasta.