Whisk together all of the marinade + dressing ingredients in a medium bowl.
Pour out half of the marinade into a large, shallow dish, bowl or freezer bag. Refrigerate the remaining half to use over the salad; make sure it doesn’t touch the raw meat.
Add the chicken to the marinade in the bowl; marinade chicken for a minimum 30 minutes or up to overnight in the refrigerator. Pro Tip: For most flavourful chicken, marinate for at least 24 hours.
While waiting for the chicken, prepare all of the salad ingredients minus the avocado and feta. Mix in a large salad bowl.
Preheat a grill or grill pan and heat 1 tablespoon of oil over medium- high heat. Remove chicken from marinade, letting excess drip off. Cook chicken until lightly charred and the thickest part reaches 165°F internal temperature, 5-6 minutes per side. Remove from heat and let rest for 5 minutes before slicing.
Remove dressing from the refrigerator and whisk again before adding to the salad.
Drizzle salad with the remaining untouched dressing. Start by drizzling some dressing all over the salad and toss gently to combine. Always remember the golden rule: You can always add more! Start with a little bit of dressing/ vinaigrette and add more if necessary. You don't want a soggy salad!
Slice and arrange chicken, avocado and feta cheese over salad. Serve with lemon wedges.