To make the tzatziki sauce; Place all of the sauce ingredients in a medium bowl and stir well to combine. Cover and keep refrigerated until ready to serve. This can be made up to 5 days in advance. Do not freeze.
To make the Greek meatball appetizers; Preheat oven to 350-degrees.
Place all of the meatball ingredients (except olive oil) in a large bowl and mix until thoroughly combined. Shape into 1″ round side meatballs. Add the oil to a large skillet.
Brown the meatballs (working in batches) on all sides.
Remove the browned meatballs and place them on a baking sheet. Bake the browned meatballs in the preheated oven for 10 minutes.
Remove the meatballs from the oven and serve them in a bowl with appetizer picks and the chilled tzatziki sauce. OR, add them to a slow cooker on “warm” to keep them warm for serving.