Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Rinse the quinoa under cold water, then combine it with 0.5 cup water in a small saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until liquid is absorbed.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper to create the marinade.
Place the chicken breast and trimmed asparagus on the prepared baking sheet.
Brush the lemon-herb marinade generously over both sides of the chicken and toss the asparagus in the remaining mixture.
Roast in the oven for 18-22 minutes, or until the chicken is cooked through to an internal temperature of 165°F and the asparagus is tender.
Fluff the cooked quinoa with a fork and serve as a base for the sliced roasted chicken and asparagus.