In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken breast in a shallow dish and pour half of the marinade over it, ensuring it is well coated.
Let the chicken marinate for at least 15 minutes to allow the flavors to penetrate the meat.
Preheat your grill or grill pan to medium-high heat and lightly grease the grates to prevent sticking.
Place the chicken on the grill and cook for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Toss the asparagus with the remaining marinade and grill for 4-5 minutes, turning occasionally until tender and slightly charred.
Serve the grilled chicken and asparagus over the warm cooked quinoa for a complete, clean-eating meal.