Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
In a small mixing bowl, whisk together the extra virgin olive oil, lemon juice, minced garlic, and dried oregano until well combined.
Place the cod fillets and the trimmed asparagus spears onto the prepared baking sheet in a single layer, ensuring they are not overcrowded.
Drizzle the lemon-herb oil mixture evenly over the fish and the asparagus, then season everything with the sea salt and black pepper.
Bake in the center of the oven for 12 to 15 minutes, or until the cod is opaque throughout and flakes easily when tested with a fork.
While the fish bakes, ensure your quinoa is warmed through if using pre-cooked leftovers.
To serve, portion the fluffy quinoa onto a plate, top with the baked cod fillet, and arrange the roasted asparagus alongside.
Garnish the entire dish with freshly chopped parsley and an extra squeeze of fresh lemon if desired.