Place all ingredients up to and including the Greek yogurt in the bowl of a food processor fitted with a chopping blade. Process until smooth and creamy.
Cut the avocado into 1/2-inch pieces and stir in. If desired, puree the avocado in so that it's smooth.
Season with salt and pepper to taste.
Serve with fresh vegetables, or as a sandwich spread.
Refrigerate any leftovers in a lidded container and use within 2-3 days.