In a small glass bowl, whisk together 0.5 tablespoon of olive oil, lemon juice, lemon zest, minced garlic, oregano, sea salt, and black pepper to create the marinade.
Place the chicken breast in a shallow dish and coat thoroughly with half of the prepared lemon-herb marinade, letting it sit for 5 minutes.
Heat the remaining 0.5 tablespoon of olive oil in a non-stick skillet over medium-high heat.
Add the chicken to the skillet and sear for 6 to 7 minutes per side until the exterior is golden brown and the internal temperature reaches 165°F.
While the chicken is cooking, toss the diced cucumber, halved cherry tomatoes, and baby spinach in a bowl with the remaining half of the marinade.
Remove the chicken from the pan and let it rest for 3 minutes before slicing into thin strips.
Assemble the bowl by placing the cooked quinoa at the base, topping it with the fresh vegetable salad and the warm, zesty chicken strips.