Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Rinse quinoa and combine with 0.5 cup water in a small pot; bring to a boil, then simmer covered for 15 minutes until tender.
Mince the garlic and finely chop the fresh parsley.
In a small bowl, whisk together olive oil, lemon juice, lemon zest, minced garlic, parsley, salt, and pepper.
Place cod fillets and trimmed asparagus on the prepared baking sheet.
Drizzle the lemon-herb mixture over both the fish and the asparagus, tossing the asparagus to coat evenly.
Bake for 12-15 minutes until the cod is opaque and flakes easily with a fork.
Fluff the quinoa with a fork and serve the zesty cod and asparagus over the grains.