Preheat your oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the diced onion and garlic, sautéing until the onion is translucent, about 3-5 minutes.
Add the ground beef to the skillet. Cook until browned, breaking it apart with a spoon, for about 5-7 minutes. Drain any excess fat.
Stir in the can of diced tomatoes (with juice), frozen mixed vegetables, beef broth, Italian seasoning, and salt and pepper. Bring the mixture to a simmer.
Once simmering, combine the cooked rice into the skillet mixture, stirring thoroughly to mix all the ingredients well.
Transfer the mixture into a greased 9x13 inch baking dish. Level it out with a spoon.
Sprinkle the shredded cheddar cheese evenly over the top.
Cover with aluminum foil and bake in the preheated oven for 20 minutes.
After 20 minutes, remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it sit for 5 minutes before serving.