01 - Preheat oven to 375°F. Lightly grease an 8x8 inch baking dish with olive oil or non-stick cooking spray.
02 - Rinse quinoa under cold water until water runs clear. Combine quinoa and water in a saucepan and bring to a boil. Reduce heat to low, cover, and simmer for 12-15 minutes until all liquid is absorbed. Fluff with a fork and 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 and translucent. Add minced garlic and cook for 1 additional minute until fragrant.
04 - Add chopped spinach to the skillet and cook, stirring frequently, for 2-3 minutes until completely wilted. Remove from heat and set aside.
05 - In a large bowl, whisk together eggs, milk, salt, black pepper, and nutmeg until well combined. Add cooked quinoa, spinach mixture, parsley, and half of the shredded cheese. Stir until evenly distributed.
06 - Transfer the mixture to the prepared baking dish, spreading it evenly. Sprinkle the remaining cheese across the top in an even layer.
07 - Bake for 25-30 minutes until the center is set and the cheese topping is golden brown. A knife inserted near the center should come out clean.
08 - Allow the bake to cool for 5 minutes before slicing into portions. Garnish with additional fresh parsley if desired. Serve while warm.