Place mince, onion, garlic and oregano in a large bowl. Season and mix to combine. Using clean hands, roll heaped tablespoons of mince mixture into balls. Repeat to make 16 balls.
Heat oil in a large non-stick frypan over medium-high heat and cook meatballs for 4 to 5 minutes or until browned and cooked through.
Spread rolls with aioli, top with rocket, tomato, cucumber and meatballs. Sprinkle with feta, olives and extra oregano. Serve with lemon wedges.
Good quality aioli is available in supermarkets and greengrocers.
You could thread the meatballs onto skewers and serve with a Greek salad and brown rice instead serving on a roll.
Make double the amount of mixture, form into patties and freeze, separated by layers of baking paper or cling wrap. Cook the patties straight from the freezer, or defrost just the amount you need for hamburger night.