Preheat your oven to 375°F and lightly grease a small 8x8 inch baking dish with the olive oil.
Finely chop the onion, bell pepper, zucchini, and broccoli into bite-sized pieces.
Heat a non-stick skillet over medium heat and sauté the chopped vegetables for 5-7 minutes until they are slightly softened and fragrant.
In a medium mixing bowl, whisk together the liquid egg whites, cottage cheese, nutritional yeast, garlic powder, dried oregano, sea salt, and black pepper until well combined.
Transfer the sautéed vegetables into the prepared baking dish, spreading them out into an even layer.
Pour the egg and cheese mixture over the vegetables, using a fork to ensure the liquid reaches the bottom and the vegetables are submerged.
Sprinkle the crumbled feta cheese evenly over the top of the casserole.
Bake in the center rack of the oven for 30 to 35 minutes, or until the eggs are fully set and the top is a beautiful golden brown.
Remove from the oven and let the casserole rest for at least 5 minutes before slicing into squares and serving.