We generally grill every 3 nights and cook enough to last us 3 meals. I buy chicken, ribs, and steaks usually, eating the steak the night it's grilled. We also buy 5lbs of potatoes and I cook them in the corningware covered casserole with butter & parsley which lasts us a few meals. We also load up on frozen veggies and just cook them in the micro every night or two. I buy the mixed bag of lettuce and a bottle of oil & vinegar to make salad.
So we don't end up cooking very much but have plenty of food to eat. last trip I purchased a really inexpensive cookie sheet at
Walmart and made some oven fried potatoes. It also came in handy when reheating the friend chicken I purchased from Trail's End

The $4 was well worth it.
FWIW - I mix up some seasonings and put them in small baggies so I can easily flavor what I'm cooking without bringing or buying the entire package.
It's really very easy to do, plus, we really enjoy it. On cooking nights, and because of having to heat the grill, I would say we start at 4pm and are finished eating by no later than 6:30pm - and as I said, it's the grill that slows us down, not the rest of the preparation.
I would say for an 8 or 9 night trip we don't spend more than 3-4 hours cooking, if that much.