Cook pasta according to package directions.
Meanwhile, cook ground beef, onion, bell pepper, Italian seasoning and garlic in a Dutch oven or large, deep skillet over medium-high heat until beef is browned, about 6 minutes, stirring to crumble. Drain, if necessary.
Stir in pasta sauce. Bring to a simmer. Stir in spinach, and cook 1 minute longer or just until spinach wilts.
Stir in pasta. Sprinkle with cheese, and stir gently until cheese melts.