Preheat your barbecue to medium-high. Layer the sheets of tin foil. Brush with 1 Tbsp. of the oil. Arrange the halibut fillets, artichokes, olives and peppers in the centre of the foil. Combine the remaining ingredients in a small bowl; spoon over the fish. Pull up the corners of the foil to form a packet, and then fold at the top to seal. Set the foil packet on one side of the barbecue. Turn the heat underneath it to medium-low; leave the other side set to medium-high. Close the lid of the barbecue and cook the halibut for 10 to 12 minutes, or until just cooked through.