Season the chicken breasts with olive oil, oregano, garlic powder, salt, and pepper.
Grill or pan-sear the chicken over medium-high heat for 6-8 minutes per side or until the internal temperature reaches 165°F (74°C). Let rest for 5 minutes before slicing.
In a small bowl, whisk together the tahini, lemon juice, and 1-2 tablespoons of warm water until a smooth, pourable consistency is achieved.
Divide the cooked quinoa into two serving bowls as a base.
Arrange the sliced chicken, chickpeas, cucumbers, tomatoes, red onions, and olives on top of the quinoa in sections.
Garnish with crumbled feta cheese and drizzle the lemon-tahini dressing over the bowls immediately before serving.