01 - Preheat oven to 375°F. Grease an 8x8 inch baking dish with olive oil or non-stick spray.
02 - Rinse quinoa thoroughly under cold water. Combine quinoa and water in a saucepan. Bring to a boil, then reduce heat, cover, and simmer for 12-15 minutes until water is absorbed and quinoa is fluffy. Set aside to cool slightly.
03 - Heat olive oil in a large skillet over medium heat. Add diced onion and cook for 2-3 minutes until softened. Add garlic and cook for another minute.
04 - Add chopped spinach to the skillet and cook, stirring, for 2-3 minutes until wilted. Remove from heat.
05 - Whisk together eggs, milk, salt, pepper, and nutmeg in a large bowl. Stir in cooked quinoa, spinach mixture, parsley, and half of the cheese until well combined.
06 - Pour mixture into the prepared baking dish. Sprinkle remaining cheese evenly on top.
07 - Bake for 25-30 minutes until center is set and top is golden brown.
08 - Let cool for 5 minutes before slicing. Garnish with extra parsley if desired. Serve warm.