In medium skillet, bring water and margarine to a boil. Slowly stir in pasta. Return to a boil.

Reduce heat to medium. Boil uncovered, 12-14 min. or until most of water is absorbed, stirring frequently. During last 5 min., add green beans or broccoli if desired.

Stir in milk, seasoning mix and tuna. Return to a boil; cook 1-2 min. or until pasta is just tender. Sauce will be thin. Let stand 3-5 min. to thicken.