Preheat oven to 350°F.
In a large bowl, beat the eggs and salt for about 5 minutes until slightly thickened and lemon-colored.
Coat a 10-inch ovenproof skillet with cooking spray; add oil, then pour in the eggs. Cook for 5 minutes over medium heat or until puffed and lightly browned on the bottom.
Transfer to the oven and bake, uncovered, for 10-12 minutes or until a knife inserted 2 inches from the edge comes out clean.
Meanwhile, dice tomato, zucchini, onion, and green pepper. Add to a large skillet, season with Italian seasoning, and sauté until tender.
Score the center of the omelet with a knife, then run the knife around the edges to loosen. Place the vegetables on one side of the omelet and sprinkle with cheese; fold the other side over, covering the filling.
Slide onto a serving plate and cut into quarters.