Heat oven to 350°F. Cook macaroni in large saucepan as directed on package for al dente pasta. Rinse under cold water; drain well.
Mix milk, egg and 5 teaspoons of the Seasoning in large bowl with wire whisk until blended. Add process cheese product and 1 cup of the shredded cheese; mix well. Stir in cooked macaroni, tomatoes and green chiles. Pour into buttered or greased 13x9-inch baking dish.
Bake 15 minutes. Remove from oven. Carefully stir until well blended. Sprinkle with remaining 1 cup shredded cheese, 1 teaspoon Seasoning and green onion. Bake 20 minutes longer or until bubbly and lightly browned on top. Let stand 5 minutes before serving.