Preheat your oven to 375°F (190°C).
Cut the eggplants in half lengthwise and scoop out the flesh, leaving a ½-inch thick shell. Chop the scooped-out flesh and set aside.
In a large bowl, combine the chopped eggplant flesh, cooked quinoa, diced tomatoes, chopped spinach, dried oregano, dried basil, salt, and black pepper. Mix well.
Stuff the eggplant shells with the mixture and place them in a baking dish.
Sprinkle the shredded mozzarella cheese on top of the stuffed eggplants.
Bake in the preheated oven for 35-40 minutes, or until the eggplants are tender and the cheese is melted and golden brown.
Remove from the oven and let cool for a few minutes before serving.