Combine ground beef, breadcrumbs, Parmesan cheese, parsley, eggs, salt, fennel seeds, and pepper. Shape into 37 (1 1/2-inch) balls. Freeze up to 1 month. When ready to use, let stand at room temperature 10 minutes. Thread meatballs 1/8 inch apart onto metal skewers. Grill, covered with grill lid, at 350° to 400° (medium-high) heat 3 to 4 minutes on each side or until centers are no longer pink, basting with barbecue sauce during last 3 minutes. Serve on skewers or buns.