In a threesome or a foursome, during any stipulated round the partners must play alternately from the teeing grounds and alternately during the play of each hole. Penalty strokes do not affect the order of play.
29-2. Match Play
If a player plays when his partner should have played, his side loses the hole.
29-3. Stroke Play
If the partners make a stroke or strokes in incorrect order, such stroke or strokes are canceled and the side incurs a penalty of two strokes. The side must correct the error by playing a ball in correct order as nearly as possible at the spot from which it first played in incorrect order (see Rule 20-5). If the side makes a stroke on the next teeing ground without first correcting the error or, in the case of the last hole of the round, leaves the putting green without declaring its intention to correct the error, the side is disqualified.
©USGA, used with permission