Preheat the oven to 400°F. Generously oil a 2-quart baking dish.
In a large bowl, whisk the eggs with ¼ cup water until well-combined and season with the salt and pepper.
Place the spinach evenly in a layer on the bottom of the baking dish. Pour the eggs over the spinach and dot the entire surface of the frittata with pieces of goat cheese. Transfer the baking dish to the oven and cook for 30 to 35 minutes or until set and beginning to color on top. Remove from the oven, let cool for at least 10 minutes, cut into squares, and serve.