Preheat the oven to 325°F. 

Place the baguette slices on a baking sheet and lightly sprinkle with granulated garlic. Toast in the oven until golden brown, 5 to 8 minutes. Set aside.

In a bowl, stir together the vinegar, olive oil, minced garlic and rosemary sprigs. Cover and refrigerate for several hours; the longer the marinade sits, the more intense the flavor.

Cut the mushrooms into 1/4- to 1/2-inch slices, the length of the crostini. Cut the cheese into 1/4-inch slices, the length of the crostini.

Prepare a medium-hot fire in a grill. 

Just before grilling, dip the mushroom slices in the marinade just long enough to cover the entire slice.

Grill the mushrooms, turning once, until nicely grill-marked, 1 to 2 minutes per side. Set aside.

Season the beef tenderloin on all sides with salt, pepper and granulated garlic. Grill the tenderloin, turning it a quarter turn every 3 minutes, until rare, or until done to your liking. Transfer the tenderloin to a cutting board and let rest for 20 minutes, then cut into thin slices.

To assemble, lay a pice of cheese on the crostini, then top with the mushrooms and beef. Sprinkle with pepper and serve.