Grilled Beef Tenderloin

1 lb fresh mushrooms, sliced
1 cup chopped green onions
1/4 cup butter or margarine, melted
1/4 cup chopped fresh parsley
1 (6-7 lb) beef tenderloin
1/2 tsp seasoned salt
1/4 tsp lemon-pepper seasoning
1 pkg (4 oz) crumbled blue cheese
1 bottle (8 oz) red wine vinegar and oil dressing
Crushed peppercorns

Sauté sliced mushrooms and green onions in butter in a large skillet until tender; drain. Stir in parsley and set mixture aside. Trim excess fat from beef tenderloin. Cut tenderloin lengthwise to 1/4" of other edge, leaving one long side connected. Sprinkle with seasoned salt and lemon-pepper seasoning. Spoon mushroom mixture into opening of tenderloin; sprinkle with blue cheese. Fold top side over stuffing. Tie tenderloin securely with heavy string at 2" intervals. Place tenderloin in a large shallow dish. Pour dressing over tenderloin, cover, and refrigerate 8 hours, basting with marinade occasionally. Remove tenderloin from marinade. Press crushed peppercorns onto each side of the tenderloin. Grill over medium-hot coals, covered or tented about 35 minutes or until meat thermometer registers 140°F (rare) or 160°F (medium). Transfer to platter, remove string, and slice to serve. Tenderloin may be baked at 350°F for about 40 minutes (same meat thermometer readings) if desired. Serves 8.