In bowl, combine barbeque sauce and lemon juice. Add prawns and scallops; let stand 30 minutes to marinate, mixing occasionally.
Thread prawns and scallops on separate skewers. Place 6 inches over hot coals. Grill 2-3 minutes, baste, turn and baste again.
Cook until prawns are pink and scallops are opaque, about 4 to 6 minutes total. Note: If using bamboo skewers, soak in water 30 minutes before use.