To make chicken: Pre-heat grill or griddle pan to medium/high heat. Rub the chicken breast with the garlic powder, italian seasoning, parsley,salt and pepper. Pour 1 tablespoon olive oil into pre-heated pan and add chicken. Cook for 7-8 minutes on each side or until the outside is golden and crispy and the inside is tender and done. Rest chicken for at least 5 minutes then slice into cubes or thin slices.
To make the dressing: Whisk yogurt, garlic and lemon juice until well combined; add salt and pepper to your taste.
To Assemble: Place chopped romaine lettuce in a big salad bowl or two individual salad plates. Top with sliced chicken, sliced avocado, and halved tomatoes, drizzle with creamy dressing to serve.