Preheat the 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 the spice mixture evenly over the chicken breasts.
Heat olive oil in a skillet over medium-high heat. Sear the chicken breasts for 2-3 minutes on each side until golden brown.
Transfer the seared chicken to the prepared baking sheet and bake for 20-25 minutes or until the internal temperature reaches 165°F. Let the chicken rest for 5 minutes before slicing.
In a large bowl, combine mixed salad greens, cherry tomatoes, cucumber, red onion, olives, and feta cheese.
Slice the cooked chicken and place it on top of the salad. Drizzle with balsamic vinaigrette and toss gently to combine.