Cook the quinoa by combining it with water or broth in a medium pot. Bring to a boil, reduce heat, cover, and simmer until fluffy, about 15 minutes.
While the quinoa cooks, preheat a grill or grill pan over medium heat.
Season chicken breasts with olive oil, garlic powder, paprika, salt, and pepper.
Grill chicken for 5 to 7 minutes per side, or until cooked through and juices run clear.
Let chicken rest for 5 minutes, then slice into strips.
Assemble bowls by dividing quinoa into servings. Top with grilled chicken, avocado, tomatoes, cucumber, and feta.
Sprinkle with herbs and drizzle with dressing if using. Serve warm or pack for meal prep.