If the ground isn't frozen & you feel energetic, sure you can move it. Plant it with top of rootball at surface level. Water it in real good & add a couple inches of mulch - fallen leaves will do. I don't know why it needs to be cut down first. I've moved a few things around myself just yesterday - the weather is rather mild.

Should be okay where you live to move... much too cold and frosty too do so with us. No need to cut back as BG says, though it might be easier to dig up if you do.

I have found established mahonias have a very large and dense rootball. You will need to dig as much of this out as possible but still expect significant root damage. Reducing the top growth will assist the plant.

Whilst the Mahonia itself may not need to be cut down I would hate the thought of trying to get close and personal with a large one - those leaves!!!!

Ha! Ha! Yes Bulbaholic, you know what I mean about those spiteful leaves LOL.
This is why I wanna cut it down folks so it will be easy to move LOL, then hopefully it will put on new growth :o))

Cut just above a leaf. Mahonias respond well to pruning, but a large plant will need TLC next year.

What would be the best time to move it? x