Preheat the grill to medium-high heat. In a small bowl, mix olive oil, garlic powder, paprika, salt, and pepper. Brush the mixture over both sides of the chicken breasts.
Grill the chicken for about 6-7 minutes per side, or until the internal temperature reaches 165°F. Remove from the grill and let it rest for 5 minutes before slicing.
While the chicken is resting, prepare the dressing by whisking together olive oil, lemon juice, orange juice, honey, salt, and pepper in a small bowl until well combined.
In a large salad bowl, combine the mixed greens, cherry tomatoes, avocado, cucumber, and red onion. Toss gently to mix.
Slice the grilled chicken and place it on top of the salad. Drizzle the citrus dressing over the salad and toss gently to combine. Sprinkle feta cheese on top if desired.
Serve immediately and enjoy!