1. Prepare grill by piling charcoal on one side of grill, leaving other side empty. (For gas grills, light only 1 side.)
2. Slice tenderloin lengthwise to, but not through, the center, leaving 1 long side connected; set aside.
3. Melt 2 tablespoons butter in a large nonstick skillet over medium-high heat. Add mushrooms and next 3 ingredients; cook 5 minutes or until tender, stirring often. Spoon mixture into opening of tenderloin, leaving a 1/2-inch border on all sides. Sprinkle cheese over mushroom mixture. Close tenderloin, and tie securely with heavy string at 2-inch intervals. Brush with melted butter.
4. Place tenderloin on unlit side of grill rack coated with cooking spray; cover and grill 45 minutes or until a meat thermometer registers 145° (medium-rare) to 160° (medium). Let stand 10 minutes before slicing.
carbo rating: 1