In a small bowl, whisk together the extra virgin 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, turning to coat evenly.
Let the chicken marinate for at least 20 minutes in the refrigerator.
Preheat your grill or a cast-iron grill pan over medium-high heat.
Place the chicken on the grill and cook for 6 to 7 minutes per side, or until the internal temperature reaches 165°F.
While the chicken cooks, toss the asparagus spears in the remaining marinade and grill them for 3 to 5 minutes until tender and lightly charred.
Remove the chicken from the grill and let it rest for 5 minutes before slicing.
Serve the sliced chicken over the warm cooked quinoa with the grilled asparagus on the side.