Start by preparing your quinoa according to package instructions. Fluff with a fork and let it cool.
In a mixing bowl, combine the quartered cherry tomatoes, diced cucumber, chopped red onion, cooked quinoa, crumbled feta cheese, sliced Kalamata olives, and chopped parsley.
Drizzle the olive oil and lemon juice over the mixture, then season with salt and pepper to taste. Gently fold the ingredients until well mixed.
Carefully take the halved avocados and spoon out a little more flesh to create a larger cavity for the filling, if desired.
Generously fill each avocado half with the Mediterranean mixture, ensuring each half is packed with flavor.
Serve immediately, or chill for about 15 minutes for the flavors to meld before serving.