Brown ground beef in a large skillet over medium heat, stirring frequently. Drain and set aside.
Drizzle olive oil into the skillet over medium heat. Saute onions until softened, about 3 minutes. Add garlic and rice, stirring frequently until rice is lightly browned. Add ground beef, oregano, chili powder, cumin, salt, black pepper, water, and tomatoes. Bring to a boil. Turn heat to low, cover, and simmer for 20 minutes or until all liquid is absorbed.