MacDonald participated in the subsequent siege of Quebec. On the night of 13 September 1759 he was part of the forlorn hope, the twenty-four volunteers leading the British attempt to climb the cliffs rising above the St. Lawrence River. It was MacDonald who responded in French to the challenge of the French guards, buying time for enough men to gather and overpower the post. This in turn allowed almost 5,000 British troops to climb the cliffs and mass on the Plains of Abraham. During the subsequent winter, MacDonald was given several independent commands, constantly harassing the French outposts surrounding Quebec.