Begin by preparing the chicken. In a small bowl, combine olive oil, garlic powder, oregano, thyme, basil, sea salt, and black pepper. Rub this mixture onto both sides of the chicken breasts.
Heat a grill pan or skillet over medium-high heat. Once hot, add the chicken breasts and cook for 7-8 minutes on each side, or until the internal temperature reaches 165°F (74°C). Remove from heat and let the chicken rest for a few minutes before slicing into strips.
While the chicken is cooking, prepare the salad base. In a large bowl, toss together mixed greens, diced cucumber, cherry tomatoes, red onion slices, Kalamata olives, and crumbled feta cheese.
For the Tzatziki Dressing, combine the Greek yogurt, grated cucumber, olive oil, lemon juice, fresh dill, and minced garlic in a bowl. Season with salt and pepper to taste and mix until well combined.
To assemble the salad, divide the mixed greens mixture among four serving plates. Top with sliced chicken and drizzle generously with Tzatziki Dressing.
Serve immediately, and enjoy a refreshing, protein-packed meal that's sure to satisfy.