Trim off and discard the tough green tops and roots from the leeks. Split leeks lengthwise and rinse thoroughly under cold water to remove all the grit. Remove ends from zucchini and quarter lengthwise.

Blanch tomatoes for 30 seconds, then transfer to a colander and cool under running water. Peel tomatoes, cut crosswise in half and gently squeeze to remove the seeds. Cut the tomatoes into quarters.

Divide the vegetables evenly among the foil squares and sprinkle each portion with basil and cider. Fold the edges of the foil together and crimp.

Place packets on the grill and cook for 15 - 20 minutes, or until vegetables are tender. Before serving, season with desired amount of salt and pepper.