PREHEAT oven to 350°F. Mix milk, tapioca and salt in medium saucepan; let stand 5 min. Bring to boil on medium heat, stirring constantly. Remove from heat. Add cheese; stir until melted. Cool slightly.
BEAT egg whites in large bowl with electric mixer on high speed until stiff but not dry; set aside. Beat egg yolks in medium bowl with wire whisk until thick and lemon colored. Add tapioca mixture; mix well. Gently stir in egg whites. Pour into 1-1/2-qt. baking dish. Place dish in large baking pan. Add enough hot water to baking pan to come 1 inch up side of baking dish.
BAKE 50 min. or until center is set. Serve immediately.