In a shallow plate whisk together all the marinade ingredients. Add the chicken breasts and toss them around making sure they are fully covered in the marinade. Cover with plastic wrap and refrigerate for about 30 minutes to up to 4 hours.
Heat up your grill so that it's around 400 F degrees.
In the mean time whisk all the dressing ingredients together in a small bowl and set aside.
In a larger bowl toss the lettuce, cucumber, red onion, bell pepper, tomatoes, and olives together.
Grill the chicken on both sides, about 5 minutes per side or until no longer pink and is cooked through. Discard remaining marinate.
Let the chicken cool for about 5 minutes before slicing it into 1/2 inch slices.
Drizzle the prepared dressing over the salad and toss well. Add the crumbled feta to the salad and mix.
Serve with the sliced chicken breast over the salad and avocado slices. Other optional sides include hummus and pita chips.
You can bake the chicken breast at 450F for 20 minutes instead of grilling.