In a 5-quart or larger slow cooker, stir together garlic, bell pepper, onion, tomatoes, chicken, broth, ½ cup cheese, basil, oregano, salt, black pepper, and red pepper flakes. Cook on low for 7-1/2 hours or on high for 3-1/2 hours.

Transfer chicken to a cutting board and use forks to coarsely shred; return to slow cooker. Stir in pasta. Cook on high for an additional 20-30 minutes or until pasta is cooked al dente.

Stir in butter, if desired. If soup becomes too thick after pasta is cooked, stir in additional broth or water until desired consistency is reached, and warm through.

Serve garnished with extra Parmesan cheese and chopped basil or parsley.