Preheat your oven to 400°F (200°C).
Dice the zucchini, red bell pepper, and red onion into small, uniform bite-sized pieces.
Heat the olive oil in a 10-inch oven-safe skillet over medium heat.
Add the diced zucchini, bell pepper, onion, and minced garlic to the skillet and sauté for 5-7 minutes until the vegetables are tender-crisp.
Add the baby spinach to the skillet and stir for 1 minute until just wilted.
In a medium bowl, whisk together the whole eggs, liquid egg whites, sea salt, black pepper, and dried oregano until well combined.
Pour the egg mixture evenly over the vegetables in the skillet, ensuring they are well distributed.
Sprinkle the crumbled feta cheese over the top of the eggs.
Transfer the skillet to the oven and bake for 10-12 minutes, or until the eggs are fully set and the edges are lightly golden.
Remove from the oven and let it sit for 2 minutes before slicing and serving.