Meanwhile, heat oil in large skillet over medium-high heat. Add onion and garlic; cook 5 minutes or until onion is tender, stirring frequently. Add beef; cook 7 minutes or until beef is crumbled and no longer pink, stirring occasionally. Drain.
Add pasta sauce to skillet; stir together. Simmer covered over medium-low heat 10 minutes or until hot. Drain spaghetti. Serve meat sauce with spaghetti. Sprinkle with cheese, if desired.