Heat a large skillet over medium heat and add olive oil. Sauté the finely chopped onion until translucent, about 5 minutes. Add ground beef, stirring until browned. Mix in rice, tomato sauce, oregano, salt, and pepper; let simmer for 10 minutes.

Preheat your oven to 180°C (350°F). Brush the bottom and sides of a rectangular baking dish with melted butter or oil.

Unroll the phyllo dough, covering it with a damp towel. Lay down the first sheet in the baking dish, brushing it lightly with melted butter. Repeat with four more sheets.

Spoon the beef and rice mixture evenly over the phyllo layers. Spread out gently with a spatula.

Cover the filling with another five sheets of phyllo, brushing each with melted butter or oil and tucking edges neatly.

Bake in the preheated oven for 40-45 minutes until golden and crisp.

Allow to cool for about 10 minutes before slicing. Garnish with parsley or dill and serve with lemon wedges.