Marinate the chicken: Whisk olive oil, lemon juice, lemon zest, garlic, oregano, basil, salt, and pepper. Coat chicken and refrigerate for at least 30 minutes.
Cook the grain base: Prepare rice or quinoa according to package directions. Fluff with a fork and set aside.
Cook the chicken: Sear chicken in a hot skillet for 5–7 minutes per side, or until it reaches 165°F. Rest for 5 minutes, then slice.
Prepare the toppings: Dice cucumber, slice tomatoes and red onion, drain olives, and crumble feta.
Make the tzatziki: Mix Greek yogurt, grated cucumber, garlic, lemon juice, olive oil, dill, and salt until smooth.
Assemble the bowls: Add rice or quinoa to bowls, then top with chicken, vegetables, olives, feta, tzatziki, and parsley.
