1. Combine the beef, green onions, chopped onion, soy sauce, sesame seeds, sugar, and oil in a medium bowl. Shape meat mixture into 1-inch balls. Transfer meatballs to a 15x10x1-inch jelly-roll pan; cover and refrigerate for 1 hour.
2. Meanwhile, soak 20 wooden skewers in water for 30 minutes. Prepare grill or preheat broiler. Thread 2 meatballs on each skewer, then grill over medium coals for 5 to 6 minutes per side or until meatballs are no longer pink. Serve immediately. Makes 20 appetizers.