Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Rinse the quinoa under cold water, then combine with 0.5 cup water in a small pot; bring to a boil, reduce to low, cover, and simmer for 15 minutes.
Snap off the woody ends of the asparagus spears and place them on one side of the prepared baking sheet.
Pat the cod fillets dry with a paper towel to ensure a better texture and place them on the other side of the sheet pan.
In a small bowl, whisk together the olive oil, minced garlic, lemon juice, lemon zest, oregano, sea salt, and black pepper.
Drizzle the lemon-herb mixture over the cod and the asparagus, using a brush or your hands to coat everything evenly.
Roast in the oven for 12 to 15 minutes, or until the cod is opaque and flakes easily with a fork and the asparagus is tender.
Fluff the quinoa with a fork and serve as a base for the flaky cod and roasted asparagus.