Heat the oil in a large skillet over medium heat. Add squash, onion, and garlic, and saute for 5 minutes. Add parsley, salt and pepper.
Layer squash mixture and tomatoes in a casserole dish. Combine egg substitute with evaporated milk, blending well and pour over vegetables. Bake for 20 to 25 minutes or until custard is set. Remove from oven, and let cool slightly before serving.