In a bowl, combine the olive oil, garlic powder, oregano, salt, and pepper. Toss the chicken breasts in the mixture until well coated.
Grill or bake the chicken until fully cooked, about 6 to 7 minutes per side. Once cooked, let it rest and slice.
Prepare the tzatziki sauce by mixing Greek yogurt, grated cucumber, minced garlic, olive oil, lemon juice, and salt in a bowl.
To assemble the bowls, divide the cooked rice or quinoa among bowls. Top with grilled chicken, cherry tomatoes, cucumber, onion, bell pepper, and feta cheese.
Drizzle with tzatziki sauce and garnish with fresh parsley. Serve immediately.
Notes
Great for leftovers and batch cooking. Squeeze excess water from cucumber for a better tzatziki.