Add olive oil to a large skillet set over medium heat. Add diced onion and garlic and season with salt and black pepper, to taste. Stir to combine and sauté, stirring occasionally, until the onion softens and develops some color, about 5 minutes.
Add ground beef to skillet and cook, stirring occasionally, until browned. Remove from heat and carefully drain excess fat from skillet.
Add taco seasoning and tomatoes with green chilis. Cook, stirring frequently until tomatoes are heated through and the beef mixture is thoroughly coated in the taco seasoning.
Remove from heat and top with shredded cheese. Cover for 1-2 minutes or until cheese is completely melted.