Heat nonstick Dutch oven or 3-quart nonstick saucepan over medium heat. Add chicken, onion and garlic; cook 4 to 6 minutes, stirring occasionally, until onion is tender.
Stir in broth, basil and salt. Heat to boiling. Increase heat to medium-high. Add pasta; cook 8 minutes, stirring occasionally.
Meanwhile, place frozen vegetables in colander or strainer; rinse with warm water until thawed. Drain well. In small bowl, mix 1 cup of the milk and the flour until smooth.
Stir vegetables, milk mixture, remaining 3 cups milk and the bell pepper into pasta mixture. Heat just to boiling, stirring frequently. Reduce heat to medium; cook 3 to 5 minutes, stirring occasionally, until soup thickens, vegetables and pasta are tender and chicken is no longer pink in center. Sprinkle individual servings with cheese.