Place the chicken breasts in an oven-safe dish and drizzle with ½ Tbsp. olive oil, turning them in the pan until coated. Season on both sides with garlic powder, paprika, ½ teaspoon salt, and pepper. Bake for 20 to 22 minutes, or until the internal cooking temperature reaches 165°F. Allow to rest 5 minutes, then slice.
While the chicken bakes, combine quinoa, 1 ½ cups water and ½ tsp. kosher salt in a saucepan. Bring to a boil, then cover, reduce heat to medium-low, and cook for 15 minutes. Remove from heat and allow to stand 5 minutes, covered, then fluff with a fork and transfer to a large bowl.
After the quinoa has cooled, fold in the tomatoes, cucumbers, green onion, and parsley. Dress with lemon juice and olive oil, then season with salt and pepper to taste.
Divide the quinoa tabbouleh into meal prep containers and top with sliced chicken breast. Cover and refrigerate up to 4 days.