In a small bowl, whisk together the olive oil, fresh lemon juice, lemon zest, minced garlic, oregano, sea salt, and black pepper to create a vibrant marinade.
Place the chicken breast in a glass dish and coat with half of the prepared marinade, allowing it to sit for 15 minutes to absorb the flavors.
Toss the trimmed asparagus spears in a separate bowl with the remaining marinade until they are evenly coated.
Preheat your grill to medium-high heat and ensure the grates are clean and lightly oiled.
Grill the chicken breast for 6 to 7 minutes per side until the exterior is beautifully seared and the internal temperature reaches 165 degrees Fahrenheit.
Add the asparagus to the grill during the final 5 minutes of cooking, turning occasionally until they are tender-crisp with light char marks.
Serve the grilled chicken and charred asparagus over a bed of warm, fluffy quinoa, drizzling any remaining juices from the chicken over the top.