Grilled Portobello Mushrooms A quick and easy recipe that makes the perfect side dish. Servings: Cook Time: 20 mins Main Ingredient: Portobello mushrooms Ingredients 1 Tbsp. olive oil 1 Tbsp. Regina® Balsamic Vinegar 1/2 lb. Portobello mushroom caps 1/8 tsp. salt black pepper Print Recipe Submit a Recipe Directions Mix olive oil and balsamic vinegar. Brush lightly over mushroom surface. Season with salt and pepper. Grill, roast or broil until tender and golden brown.