Preheat oven to 375°F (190°C) and lightly grease a 9×9-inch baking dish with olive oil.
Whisk eggs in a large bowl until smooth, then stir in cooked quinoa, spinach, cherry tomatoes, feta, salt, pepper, and half of the herbs.
Pour mixture evenly into prepared baking dish. Smooth the top with a spatula.
Bake for 25–30 minutes until eggs are set and the top is lightly golden. Check doneness by inserting a toothpick; it should come out clean.
Remove from oven and let rest for 5 minutes to finish cooking gently and make slicing easier.
Slice into squares and serve warm, garnished with remaining herbs, avocado slices, and fresh berries.
Optional: Pair with a smoothie bowl, fresh juice, or light coffee for a full heartumental brunch experience.