Veggies, overall, can be tough for dogs to digest. Steaming them "starts" the digestion process, so this makes it easier on their system, pureeing them makes it even easier. So, when I was homecooking (we now do raw) - I steamed, then pureed green beans (the greens alkalize the system). I would not feed corn.
You do lose some nutrients from steaming, but you can add those back in through supplementation. It is NOT worth stressing your dog's digestion (if they are having a tough time w/ veg, as many do) - as that can lead to all sort of trouble for some.
Don't micro the meat - it actually alters the "makeup" of the meat. I wouldn't do that at all. If you need convenience, maybe buy a toaster oven and use that to warm stuff up.
