Preheat oven to 400°.
Bring 1 cup chicken broth to a boil in a medium saucepan; gradually stir in uncooked couscous. Remove from heat; cover and let stand 5 minutes. Fluff couscous with a fork.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add squash, onions, basil, oregano, and garlic; sauté 3 minutes or until squash is tender. Set aside.
Combine fontina and Parmigiano-Reggiano; set aside. Combine couscous, squash mixture, and half of cheese mixture in a large bowl; stir in remaining chicken broth, egg substitute, salt, and pepper. Spoon mixture into an 8 x 8-inch baking dish lightly coated with cooking spray. Top with remaining cheese mixture. Bake at 400° for 35 minutes or until golden. Serve warm.