Preheat the oven to 375°F (190°C).
Slice the eggplants in half lengthwise and scoop out the flesh.
Chop the scooped-out eggplant flesh and set aside.
In a skillet, sauté onions and garlic until translucent.
Add the chopped eggplant flesh and bell peppers to the skillet, cooking for about 5 minutes.
Stir in cooked quinoa, diced tomatoes, oregano, paprika, salt, and pepper; cook for another 3-5 minutes.
Spoon the filling into the prepared eggplant halves.
Top with grated cheese if desired.
Place the stuffed eggplants in a baking dish and drizzle with olive oil.
Bake in the preheated oven for 25-30 minutes, until the eggplants are tender.