1. Place 6 pieces of foil onto a work surface. Slice squash horizontally into 1/2" thick rings. Remove seeds and place one squash slice onto each sheet of foil.
2. Place 3 similar-sized scallop pieces on top of each squash ring. Place 1 Tbsp. butter and sprinkle 2 tsps. brown sugar on top of each scallop and squash combination.
3. Double-fold top edge and ends of foil to form a packet. Make sure fold is tight so juices do not leak. Grill packets on medium heat 7 to 9 minutes, turning halfway through cooking time.
Slowly open packets and season with lemon juice, salt and pepper. Crumble extra foil to form a bowl and serve immediately.