Grilled Portobello Mushroom Burgers - Martin's Famous Potato Rolls and Bread

Ingredients

• 4 portobello mushroom caps
• 2 Tbsp balsamic vinegar
• 1 Tbsp low sodium soy sauce
• 1 Tbsp olive oil
• 1 Tbsp chopped rosemary
• 1-1/2 tsp steak seasoning like Montreal Steak Grill Mates
• 4 thick slices red onion
• 4 oz reduced fat Swiss, sliced thin (Alpine lace)
• 4 thin slices tomato
• 1/2 avocado, sliced thin
• baby spinach
• 4 Martin’s 12-Sliced Potato Rolls