Prepare the Marinade: In a bowl, whisk together olive oil, lemon juice, garlic, dried oregano, ground cumin, salt, and black pepper.
Marinate the Chicken: Add chicken to the marinade, ensuring each piece is evenly coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor.
Cook the Chicken: Heat a grill pan or skillet over medium-high heat. Cook the chicken for 5-7 minutes per side, or until the internal temperature reaches 165°F (75°C). Let rest for 5 minutes before slicing.
Make the Tzatziki Sauce: Grate cucumber and squeeze out excess liquid using paper towels. In a bowl, combine Greek yogurt, grated cucumber, minced garlic, lemon juice, olive oil, fresh dill, and salt. Stir well and refrigerate until ready to use.
Prepare the Rice: Toss cooked rice, quinoa, or cauliflower rice with a drizzle of olive oil, dried oregano, and a pinch of salt for added flavor.
Assemble the Bowls: Start with a base of seasoned rice. Top with sliced chicken, cherry tomatoes, diced cucumber, sliced red onion, Kalamata olives, and crumbled feta cheese.
Drizzle & Garnish: Spoon tzatziki sauce generously over the bowl and garnish with fresh parsley. Serve with warm pita bread or naan on the side if desired.