Place the quinoa, stock and a pinch of salt in a small saucepan and bring to a boil.
Reduce heat to a gentle simmer, cover, and cook for 15 minutes or until the liquid is absorbed and quinoa is tender.
Remove from heat, keep covered for about 2 minutes, then fluff with a fork and stir in 1/2 lemon juice; set aside to cool slightly.
Heat 1 tablespoon oil in a large skillet or nonstick pan over medium-high heat.
Add the chicken fillets, balsamic vinegar, 1/2 lemon juice, 1 teaspoon stock powder and garlic powder (or crushed garlic) and sauté until golden and cooked through, turning so both sides are browned.
Remove chicken from the pan, let it rest briefly, then slice into 1-inch strips.
Whisk together 2 tablespoons garlic olive oil and 2 teaspoons balsamic vinegar in a small bowl to make the dressing.
In a large salad bowl, combine the shredded lettuce, halved grape tomatoes, sliced red onion, kalamata olives, feta and parsley.
Top the salad with the sliced chicken and the cooked lemon quinoa, drizzle with the dressing, toss gently to combine, and serve with lemon wedges if desired.