Grillmistress: Foil Potatoes

So.
J believes that there should be starch with most meals.  He has this bizarre love/hate relationship with carbs that I totally don't get.  He might not want pizza at dinner because there are "too many carbs", but then will add 3 packets of sugar to a cup of coffee.  Although it's kind of the pot calling the kettle black...I just know I don't need the number of refined carbs that I eat in sugar or flour form.
Ahem.  But, he expects either potatoes, rice, or pasta as a side when I make dinner at home.  Here's what we like to do with potatoes in the summer when we're grilling.  I present to you now Sarah's foil packet potatoes:

Slice up a potato per person, or the number that looks good to you.  I'll also quarter baby potatoes, or I saw some at the market today that were about half the size of an egg yolk.  I'd scrub them and use them whole.  I prefer sliced.  J likes cubed.  When he starts doing the potatoes, we'll have cubed.
Mix the slices with spices:  I use a mix of Epicure spice mixes, including three onion, lemon dilly, and garlic herb.  I've never tried Penzey's Sunny Paris, but they'd be interesting.  Add a splash of oil - olive, canola, it's not really important.
Pour onto a doubled piece of greased foil.  I add a small square of butter on top.

Fold up the foil down the center and at both ends, leaving some headroom for steam.

I toss the packet on the upper grill when I start the grill.  Things that I cook on my own are not known to be an exact science.  I find if I start the potatoes right away, they're done about the same time as the meat.  I'm all about timing things to be done together.
Cook until you think they're done.  Don't peek!  The steam will escape.  I find if I let the grill warm up 10 minutes, and then you cook your steak under the potatoes, take the steak off, turn the BBQ off, take the meat in, and come back for the potatoes, they're done when you open the package.  J likes crunchy potatoes.  I totally don't.  This is a good consistency for both of us.