When i was going to law school, i created something I called 4 Can Cassarole:
1 lg can of potatoes
1 can of green beans
1 can of tomatoes
1 can of Cream of Mushroom soup.
Dump in pot in order. Season to taste. Bake.
It was literally an open cans, dump in pot Cassarole, so prep time is entirely dependent upon the speed of your can opener.
Today, however, I'm a bit less time sensitive, so I always use fresh potatoes, usually use fresh or frozen green beans, and occasionally use fresh tomatoes.
In addition, since I don't have the liquid from the canned potatoes & green beans to use, I add a can of low-sodium chicken broth. Sometimes, I add fresh chopped mushrooms for additional flavor.