Prep Time: 10
Cook Time: 10
Serves: Serves: 4
Brush 4 tablespoons dressing over mushroom caps and onions; season with salt and pepper.
Grill mushroom and onion slices over medium coals 4 minutes per side or until tender. Sprinkle cheese over stem sides of mushroom caps.
Brush cut-sides of rolls with remaining 2 tablespoons dressing. Grill to toast lightly. Place spinach on roll; top with onion slices, mushroom caps and other roll half.