Combine chicken, 2 tbsp lemon juice, 1/2 tbsp olive oil, and garlic in a zip bag. Turn to coat. Allow to stand for 5 minutes. Heat a grill pan over medium heat, coat pan with cooking spray. Remove chicken from bag and discard marinade. Sprinkle chicken with 1/4 tsp salt and 1/4 tsp pepper. Grill 5-6 minutes on each side, until chicken is done. While chicken cooks, heat rice according to package directions. Combine remaining 2 tbsp lemon juice and remaining 1/2 tbsp oil in a bowl and whisk together. Add rice, black olives, tomatoes, lemon zest, green onions, remaining salt and pepper, and feta cheese. Toss to combine. Serve rice with chicken.