Stir the marinade yogurt, lemon juice, garlic, parsley, olive oil, oregano, paprika, cumin, coriander, salt, and pepper together.
Add the chicken pieces and toss until coated, then let the chicken marinate for at least 20 minutes.
Mix the squeezed shredded cucumber with Greek yogurt, lemon juice, dill, salt, and pepper to make the tzatziki.
Prep the tomatoes, diced cucumber, red onion, olives, and feta for topping the bowls.
Cook the chicken in a hot skillet in a single layer until browned and cooked through to 165°F.
Divide the brown rice among bowls, then top with chicken, fresh vegetables, olives, feta, and tzatziki.
Serve warm with extra dill, parsley, lemon juice, or black pepper if desired.