Preheat your oven to 350°F.
In a large skillet over medium heat, brown the ground beef with the chopped onion and minced garlic until the beef is fully cooked and the onion is translucent, about 5-7 minutes. Drain any excess fat.
Add the chopped cabbage to the skillet and cook for an additional 5 minutes, stirring occasionally, until the cabbage begins to soften.
Stir in the diced tomatoes (with juice), cooked rice, oregano, salt, and black pepper. Mix well and let it simmer for another 5 minutes.
Transfer the mixture to a greased 9x13-inch baking dish. Spread it evenly and top with shredded cheddar cheese.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Let the dish cool for a few minutes before serving.