From Epicurious.com; 10 minutes prep time and 5 minutes to grill

Toss scallions with oil, salt, and pepper in a large bowl. Line up scallions side by side on a work surface and thread skewers, 1 at a time, crosswise through all scallions to form a solid rectangle. (Skewers should be inserted about 2 inches from each end.) Grill on lightly oiled grill rack, uncovered, turning over once or twice, until softened and charred in patches, 4 to 5 minutes total. Transfer scallions to a platter and squeeze lemon evenly over them, then remove skewers.