Heat oven to 375°F (190°C). Line a baking sheet with parchment or grease lightly.
In a large bowl, combine ground chicken, Parmesan, breadcrumbs, parsley, garlic, egg, oregano, salt, pepper, and optional veggies. Mix gently.
Pour in milk and mix just until combined. The mixture should be soft but shapeable.
Divide into four portions. Form into 4x2-inch mini loaves and place on the baking sheet.
Spoon olive oil over the tops for browning and moisture.
Bake 25–30 minutes until golden and cooked through (165°F/74°C inside).
Let rest 5 minutes before serving to retain juices.