Preheat the oven to 375 degrees.
Lightly grease a 9x13-inch casserole dish with oil.
Add the ground beef and chopped onion to a large skillet and cook over medium-high heat until the beef is no longer pink and the onion is tender. Drain excess grease.
Stir Worcestershire sauce into the ground beef mixture and spread evenly in the prepared pan.
Evenly spread the drained green beans over the meat mixture; season with salt and pepper.
Spread the condensed cream of mushroom soup evenly over the green beans, then sprinkle the cheese over the top.
Arrange the frozen tater tots in an even layer across the top.
Bake 45 minutes or until the casserole bubbles and the tots become golden brown and crisp.
Enjoy!