I think it depends on how intact the various ingredients are before you freeze it. Freezing bursts cell walls and tends to make things mushy.

Considering how much running around DH and I do, I'm always throwing leftovers into the freezer when we can't finish them before a trip. Most things freeze just fine, but we tend to eat a lot of one-pot meals, too.

If you're talking about a salad with diced fresh tomatoes, tomatoes aren't going to survive freezing very well, but on the other hand they won't keep in the fridge all that long either. Same with cooked beans - if their skins aren't split now, many of them will be after freezing.

If your dish is already a cooked casserole, it should freeze fine. Alternatively, it sounds like even if it's a salad now, it could be turned into a casserole without too much tweaking? Warm, brown the top, maybe a little cheese or bechamel (dairy or soy as you choose)?