Remove the inside ribbing of the mushroom caps with a spoon. Brush olive oil on both sides of the mushrooms and season with salt and pepper.
2 tablespoons olive oil, 5 large portobello mushroom caps
Grill the mushroom caps until they've shrunk and are tender, about 5-7 minutes.
Remove from grill and with a tablespoon, spoon marinara sauce on inside of the mushroom then top with desired toppings and put on grill again and heat up until cheese has melted.