Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Trim the woody ends off the asparagus and place them on one side of the baking sheet.
Pat the cod fillets dry with a paper towel and place them on the other side of the baking sheet.
In a small bowl, whisk together the olive oil, minced garlic, dried oregano, sea salt, and black pepper.
Drizzle the herb oil mixture evenly over both the cod and the asparagus, tossing the asparagus slightly to coat.
Slice the half lemon into thin rounds and place them directly on top of the cod fillets.
Bake for 12 to 15 minutes, or until the cod is opaque and flakes easily with a fork and the asparagus is tender-crisp.
Serve the roasted fish and vegetables over a bed of warm, fluffy cooked quinoa.