Heat gas or charcoal grill. In medium bowl, mix beef, onion, parsley and seasoned salt. Divide into 16 portions. Shape each portion into a ball and flatten to 1/2-inch-thick patty, about 1 1/2 inches in diameter. On each of 4 (12-inch) metal skewers, thread 4 patties horizontally, leaving space between each.
Place patties on grill. Cover grill; cook over medium heat 8 to 10 minutes, turning once, until patties are no longer pink in center (160°F).
Top each burger with cheese piece. Place each burger on toast square. Top with tomato slice and another toast square. Place pickle slice on top; spear with toothpick to hold layers together. Serve with ketchup and mustard for dipping.