Preheat the oven to 400 degrees F. Lightly coat two 6-ounce ramekins with cooking spray.
Heat the olive oil in a medium skillet set over medium heat.
Add the onion and cook until softened and just starting to brown, 5 to 6 minutes. Add the zucchini and cook for 2 additional minutes.
Divide the vegetable mixture evenly between the two ramekins. Top with the Gruyere cheese.
In a small bowl, whisk together the eggs, egg white and water. Pour the mixture over the vegetables in the ramekins. Season with salt and pepper.
Place the ramekins on a baking sheet and transfer to the oven.
Bake until the eggs are set and just starting to brown, about 20 minutes.
Garnish with parsley. Serve.
Notes
Please note that I am not a medical or nutritional professional. I provide nutritional information for my recipes as a courtesy to my readers. It is calculated using the LoseIt! calculator. While I attempt to provide information that is as accurate as possible, you should calculate the nutritional information independently before relying on it.