Do you know where exactly the guy is stationed? If he's on a small FOB or something (likely if he's Infantry, MP, or something like that) he probably won't have access to a commissary. Our FOB just has a smallish PX. Decent, but all packaged food. Honestly, I'd be surprised to find fresh food, esp good steaks, even on the larger FOBs in the IZ.
To warn you, your mail will be abused. It will be thrown around, stored in a hot conex (well, it is cooler this time of year), and possibly held up for a few weeks. Don't send anything that can't handle abuse or at least isn't well packaged (think leaks).
You could send him something vacuum sealed or something maybe??? Just thinking. The next question is where is he going to cook it?
Anyway, I second the suggestion for jerky or summer sausage. The steaks may be less than realistic.