In a large bowl, combine the ground lamb, ground beef, breadcrumbs, milk, beaten egg, minced garlic, chopped parsley, chopped mint, dried oregano, salt, and pepper. Mix gently with your hands until just combined. Be careful not to overmix, as this can make the meatballs tough.
Shape the mixture into small meatballs, about 1 to 1.5 inches in diameter.
Heat the olive oil in a large skillet over medium-high heat. Add the meatballs in batches, being careful not to overcrowd the pan. Cook for 8-10 minutes, turning occasionally, until browned on all sides and cooked through. You may need to adjust the heat to prevent burning.
Remove the meatballs from the skillet and place them on a plate lined with paper towels to drain any excess grease. Serve hot.
Notes
These Greek meatballs are delicious served with a side of tzatziki sauce, a fresh Greek salad, or as part of a mezze platter. They can also be added to pasta dishes or pita bread.