Mix the ingredients with marinade mix and divide into 2 bowls. Add prawns into one bowl and vegetables in the other. Mix and set aside for 2-3 hours.
Soak the skewers in water to avoid getting them burn when barbequing.
On the skewers, alternately thread the prawn, green pepper, tomato and onion.
Heat up a barbeque plate until hot and maintain at medium high heat. Cook skewers, basting with remaining marinade mix for 1-2 minutes each side, until cooked. Serve.