This is one of those great recipes that you can use your favorite vegetables. Just remember to cook veggies like carrots first since they take longer than say the potatoes. Of course, you can substitute all the vegetables with a couple of cans of Veg-All, but I like this version better with fresh/frozen veggies.
This can also be made ahead and refrigerated and then cooked in the oven -OR- make the vegetable filling and freeze up to a couple of months. When ready to complete, just thaw filling and bake with the potatoes and cheese.