We wipe the Portobellos with a damp cloth and remove the stems with a paring knife. Using a teaspoon, we scrape away the gills onto a paper towel and discard. The mushroom caps are placed on a dinner plate.
We slice the roasted red pepper and crumble the cheese into a bowl.
We rub the three caps on both sides with the olive oil and sprinkle with salt and pepper. We place the mushrooms gill-side down on the grill for about four minutes. We flip and top with the roasted pepper and blue cheese. The “pizzas” are cooked for another couple of minutes, with the grill cover down. The mushrooms should be tender and the cheese melted.