Preheat your oven to 400°F (200°C) and lightly grease a small baking dish with a touch of olive oil.
Place the diced bell peppers and zucchini on a parchment-lined baking sheet, toss with olive oil, sea salt, black pepper, and garlic powder.
Roast the vegetables for 12-15 minutes until they are slightly tender and starting to brown at the edges.
Remove the tray from the oven and toss in the baby spinach, letting the residual heat wilt the leaves slightly.
Transfer the roasted vegetables into the prepared baking dish, spreading them out into an even layer.
In a medium bowl, whisk together the large eggs and liquid egg whites until well combined and slightly frothy.
Pour the egg mixture over the roasted vegetables and sprinkle the crumbled feta cheese evenly across the top.
Place the dish in the oven and bake for 18-22 minutes, or until the eggs are set in the center and the top is golden.
Allow the dish to cool for a few minutes before slicing into hearty portions and serving warm.