1. Combine first 6 ingredients in a large bowl. Set aside 1/3 cup marinade.
2. Slice squid in half lengthwise. Stir into marinade. Cover and marinate 30 minutes.
3. Stir prawns into marinade with squid; cover and marinate 30 more minutes.
4. Grill prawns over medium-high heat (350° to 400°) for 2 to 3 minutes on each side. Grill squid 1 to 2 minutes on each side or until opaque. Place on a serving platter and drizzle with reserved marinade.