In a large pan over medium heat, add oil and sauté onions until translucent. Add ground beef with Worcestershire, garlic, salt and pepper. Cook until browned and crumbly.
Mix in peas and corn and cook for 3 mins.
Add gravy mix and ¾ cup water. Increase heat to medium-high and cook while stirring continuously until gravy is thickened, approx. 3 mins.
Transfer beef mixture to 9x13 baking dish in an even layer. Top with potatoes, and then with cheese.
Bake in preheated over for 15 mins or until cheese is melted.