Preheat the oven to 375°F (190°C) and coat a 9x9-inch ceramic baking dish with non-stick cooking spray.
In a large mixing bowl, whisk the eggs and liquid egg whites together until fully emulsified.
Incorporate the cottage cheese and nutritional yeast into the egg mixture, stirring until evenly distributed.
Season the mixture with garlic powder, salt, and black pepper.
Fold in the chopped broccoli, baby spinach, diced red bell pepper, and onions until the vegetables are thoroughly coated in the protein base.
Transfer the mixture into the prepared baking dish and level the surface with a spatula.
Evenly distribute the shredded mozzarella cheese over the top of the mixture.
Bake for 35 to 40 minutes, or until the internal temperature reaches 160°F (71°C) and the top is lightly browned.
Remove from the oven and allow the bake to set for 5 to 10 minutes before slicing into four equal portions.