Cook pasta shells according to package directions. Meanwhile, in a skillet, cook the beef, onion and garlic over medium heat until meat is no longer pink; drain. Stir in the tomato sauce, tomatoes, 1/2 teaspoon oregano and basil. Bring to a boil. Reduce heat; simmer, uncovered, for 10-15 minutes.
In a large bowl, combine the eggs, cottage cheese, spinach, mozzarella cheese, Parmesan cheese, seasoned salt and remaining oregano. Drain pasta shells; cool slightly. Stuff with cheese mixture.
Spread 1 cup of meat sauce into each of 2 greased 11x7-in. baking dishes; arrange shells over sauce in a single layer. Pour remaining meat sauce over the shells. Cover and bake at 350° for 40-50 minutes or until a thermometer reads 160°.