In a bowl, mix olive oil, oregano, garlic powder, onion powder, salt, and pepper. Add the chicken breasts, coating them well in the marinade. Cover and let it marinate in the refrigerator for at least 30 minutes.
Preheat a grill or stovetop skillet over medium-high heat. Remove the chicken from the marinade and cook for about 6-7 minutes per side, or until fully cooked and golden brown. Remove from heat and allow to rest for 5 minutes before slicing into strips.
In serving bowls, place a generous serving of cooked quinoa or rice.
Top the grains with sliced grilled chicken, halved cherry tomatoes, diced cucumber, sliced red onion, and a handful of lettuce or spinach.
Sprinkle crumbled feta cheese and sliced kalamata olives over the top.
Finally, add a generous drizzle of tzatziki sauce on top of the bowls for a refreshing flavor.
Notes
Let the chicken marinate for longer for more flavor.