Place ground beef in 1 1/2-quart casserole. Cook on full power 4 to 5 minutes, or until beef is no longer pink. Stir halfway through cooking time. Drain.
Add spaghetti sauce, Italian seasoning, and garlic salt to meat. Set aside.
Combine eggs, ricotta cheese, 1/4 cup parmesan cheese, 1/2 cup Mozzarella cheese, parsley flakes, onion, salt and pepper. Stuff each cooked manicotti shell with egg-cheese mixture.
Place half of meat mixture into 2-quart utility dish. Overlap stuffed manicotti shells on top of meat mixture and then top with remaining meat mixture. Cover loosely with heavy-duty plastic wrap. Cook, covered, on full power for 13 to 16 minutes, or until heated through. Sprinkle remaining Mozzarella and Parmesan cheeses over top during last minute of cooking time.