Stuffing tenderloin with a mixture of dry bread, cheese, bacon, and vegetables can up the ante considerably. If you want to kick grilled tenderloin up a couple of notches, stuffing it is the way to go. You can experiment with ingredients that you like, or go with a few tried-and-true standards.
Bacon-mushroom stuffing: In a skillet, crisp up 3-4 slices of bacon, then add two cups of white button mushrooms, and a pinch of salt. Let the mushrooms sit untouched for one minute, then stir to coat them in the mixture and cook until soft. Add 2 cloves of minced garlic and cook until soft. To this, add 2-3 tablespoons of dried breadcrumbs, and a handful of fresh chopped parsley to complete the stuffing mixture. Italian Spinach stuffing: In a food processor, add a cup of fresh baby spinach leaves, a half cup of fresh basil, two cloves of garlic, and 2-4 tablespoons of grated parmesan cheese. Add a pinch of crushed red pepper, Italian seasoning, and a drizzle of balsamic vinegar to finish the stuffing. Bacon-Wrapped Stuffed Tenderloin: In a bowl, combine a small finely chopped onion, 1-2 stalks of celery, 1-2 slices of dry toast, torn into small pieces, 3 tablespoons of melted butter, and salt, pepper, and oregano. Use this to stuff the tenderloin, then roll it up and wrap the whole thing with 6-8 strips of bacon, around the width of the meat. Tie it and grill it as normal. It's a delicious combo.