Fill with some "setting type" joint compound (comes in bags, and sometimes in a small box if it's "5" (i.e. sets in 5 minutes). Mix it thick and put it in, use some backing if possible. Finish coat with regular (drying) compound.

I would take dwall guy's advise except i would use seam tape. Perforated paper, not mesh.

I read somewhere on the forums here that in some cases it is easier just to take out a larger, perhaps square, section to get to the framing and just put a new section of properly supported drywall up. Maybe putting 2" wood nailers where necessary for backing.Thinking about it, it seems obviously true, instead of all the fragile patching. Then just drill new holes.

Thanks for the suggestions. BTW, the subject line was wrong. The hole is 1 inch off, not 1 foot.

"I would take dwall guy's advise except i would use seam tape. Perforated paper, not mesh."

Paper tape and setting compound is a bad combination.
Setting compound can easily be mixed thick enough to fill even decent size gaps with no support (and really large gaps if it has solid support).

Setting compound does not harden by drying out (it hardens by chemical reaction) so it does not shrink like pre-mixed mud (unless you add a lot of water when mixing the setting).

Thanks, Brickeye. I'm going to have to get familiar with setting compounds vs joint compounds one of these days. Back in the older days we mixed "fixall" in with the joint compound to speed up and harden the tape coat, usually when mudding in the winter/colder months.

The Garden Web entry box for the original subject will always convert " to ' so you need to use "in.", etc.

My boss likes to use expanding foam for problems like this. After it cures you cut it off with a large razor blade, then tape as normal. It won't sag like a huge glob of compound, doesn't take an extra day to dry fully.
Casey