Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a small bowl, mix together garlic powder, onion powder, paprika, oregano, salt, and pepper. Rub this spice mixture all over the chicken breasts.
Heat olive oil in a large skillet over medium-high heat. Add the seasoned chicken breasts and sear for about 3-4 minutes on each side until golden brown.
Transfer the seared chicken to the prepared baking sheet and bake in the preheated oven for 15-20 minutes, or until the internal temperature reaches 165°F. Remove from the oven and let it rest for 5 minutes before slicing.
In a large salad bowl, combine mixed greens, cherry tomatoes, cucumber, red onion, olives, and feta cheese.
Slice the rested chicken and place it on top of the salad. Drizzle with balsamic vinaigrette and toss gently to combine.