Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Rinse the quinoa under cold water, then combine it with 0.5 cup of water in a small saucepan; bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until fluffy.
Trim the woody ends off the asparagus and place the spears on one side of the prepared baking sheet.
Place the cod fillet on the other side of the baking sheet.
In a small bowl, whisk together the extra virgin olive oil, minced garlic, dried oregano, sea salt, and black pepper.
Drizzle the herb oil mixture over both the cod and the asparagus, tossing the asparagus gently to ensure even coating.
Slice the half lemon into thin rounds and arrange them across the top of the cod fillet.
Bake for 12 to 15 minutes, or until the cod is opaque and flakes easily with a fork and the asparagus is tender.
Fluff the cooked quinoa with a fork and serve it as a base for the baked cod and asparagus.