In a skillet on the stove, heat diced onions in 1 tablespoon of olive oil for about 2-3 minutes until opaque and soft.
Add in ground beef and cook until browned. Drain grease. Break up the beef as you cook so that there are no large chunks.
Transfer beef and onions to large mixing bowl. Add in the soup, sour cream, corn, and ¾ cup of the cheese. Stir well.
Transfer the beef and onions to a large mixing bowl and add in the rest of the ingredients (minus the tater tots). Reserve about ¼ cup of cheese for the top if desired.
Pour the creamy mixture into a greased 9x13 baking dish.
Top with an even layer of frozen tater tots.
Sprinkle the top with the reserved cheese.
Bake at 350 degrees F for 1 hour.