Preheat oven to 400°F and line a baking sheet with parchment paper.
Rinse the quinoa under cold water, then combine with 0.5 cup water in a small saucepan; bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper.
Place the cod fillet and the asparagus on the prepared baking sheet.
Pour the lemon-herb mixture over the cod and asparagus, ensuring the asparagus is evenly coated.
Bake for 12 to 15 minutes until the cod is opaque and flakes easily with a fork and the asparagus is tender.
Fluff the quinoa with a fork and serve the cod and vegetables over the grains.