Light a grill or preheat the oven to 475°. In a medium saucepan of boiling water, blanch the corn for 1 minute; drain.
Mound the corn on half of a 2-foot piece of foil, leaving a 1-inch border around the sides. Tuck the bacon among the kernels. Fold the other half of the foil over the corn and make small folds around the edges to seal. Grill for 6 to 8 minutes, or until the packet is puffed. Alternatively, set the packet on a baking sheet and bake on the bottom of the oven for about 10 minutes. Open the packet and stir in the scallion rounds.