Slice the eggplants lengthwise, about ⅓–½ inches (1 cm) thick. Coat with olive oil on both sides and place on a baking sheet lined with parchment paper. Bake for about 20 minutes or until slightly browned.
Fry garlic and onion in remaining olive oil until softened, about 3-4 minutes.
Add beef and sauté until cooked through. Add tomato sauce, and season with salt and pepper. Let simmer for 10 minutes, or until warmed through.
Remove the eggplant slices from the oven and spread the meat mixture on top. Sprinkle with cheese and oregano. Place in the oven for about 10 minutes or until the cheese has melted.