Halve the tomatoes and peppers lengthways and remove the seeds, remove the stalks from the mushrooms. Finely dice the garlic, mushroom stalks, feta cheese and mozzarella.
Mix the feta cheese and the mushroom cubes with oregano, half of the garlic, salt and pepper. Mix the mozzarella with the basil and the remaining garlic, season too.
Fill the prepared vegetables with 1 tablespoon each of the feta cheese and mozzarella mixture. The boats are then placed on the grill rim until the cheese has melted.