Pat the chicken breast dry with a paper towel and season both sides evenly with sea salt, black pepper, and dried oregano.
Heat half of the olive oil in a large stainless steel or cast iron skillet over medium-high heat until shimmering.
Place the chicken in the pan and sear for 6-7 minutes per side until deeply golden brown and the internal temperature reaches 165°F.
Remove the chicken from the skillet and transfer to a clean plate to rest for 5 minutes.
In the same skillet, add the remaining olive oil along with the minced garlic, sliced zucchini, and trimmed asparagus spears.
Sauté the vegetables for 4-5 minutes, stirring occasionally, until they are tender-crisp and show slight charred marks.
Stir in the cooked quinoa and lemon juice, tossing everything together for 1-2 minutes until the quinoa is warmed through and well-coated.
Slice the rested chicken into strips and serve over the vegetable-quinoa medley, garnished with a sprinkle of fresh chopped parsley.