COOK pasta as directed on package.
MEANWHILE, cook and stir onion in hot oil on medium-high heat for 5 minutes or until onion is tender. Add dressing mix and water; stir until well blended. Add vegetables and beans; mix lightly. Bring to boil. Reduce heat to medium-low; cover. Simmer 10 minutes.
TOSS vegetable mixture with pasta; sprinkle with cheese.