To make marinade, put oregano, garlic, oil and vinegar in a bowl and whisk to combine.
Add shrimp and toss to coat. Cover and refrigerate for at least 1hour or overnight. Drain shrimp and reserve marinade. Cut each bacon rasher into three pieces, wrap a piece of bacon around each shrimp and secure with a wooden toothpick or cocktail stick
Cook shrimp under a preheated medium grill or on the barbecue, turning occasionally and brushing with reserved marinade for 5 minutes or til bacon is crisp and shrimp are cooked. Makes about 24