Preheat oven to 350°F; lightly grease a 9x13-inch baking dish.

Halve attached rolls horizontally without separating; place bottom half in dish.

Layer ham and Swiss evenly; replace roll tops.

Whisk butter, mustard, poppy seeds, onion, and Worcestershire in small bowl until combined.

Pour evenly over roll tops; brush to cover all surfaces.

Cover with foil; bake 15 minutes, then uncover and bake 5 minutes until tops are golden brown.

Cool 5 minutes; cut individual sliders and serve warm.