Heat oil in large ovenproof nonstick skillet on medium heat. Add onion, zucchini and bell pepper; cook and stir 2 to 3 minutes or until vegetables are tender.
Beat eggs, milk and Seasoning in medium bowl. Pour into skillet. Cook on medium-low heat without stirring 5 minutes or until eggs are set on bottom. Arrange sliced tomatoes on top of egg mixture. Sprinkle with cheese.
Broil 4 to 5 minutes or until eggs are set and cheese is lightly browned.