Rinse the quinoa well and combine with water and 2/3 tsp salt in a pot. Bring to a boil, then cover and simmer until water is absorbed; fluff with a fork.
While the quinoa cooks, toss zucchini, bell pepper, and red onion with 2-3 tbsp olive oil.
Grill the vegetables over medium-high heat until tender and slightly charred.
In a blender or food processor, combine fresh basil, lemon juice, lemon zest, 4 tbsp olive oil, and 1/4 tsp salt. Process until smooth.
In a large bowl, combine the cooked quinoa, grilled vegetables, cherry tomatoes, sun-dried tomatoes, and Kalamata olives.
Pour the herb dressing over the salad and toss gently to coat.
Top with crumbled feta cheese before serving.