In small bowl, combine spinach, garlic powder and lemon-pepper seasoning; mix well.
Place beef sirloin on cutting board. (Beef should be rectangular in shape). Sprinkle with pepper. Spread spinach mixture evenly over beef. Beginning with long edge, roll up jelly-roll fashion. To secure roll-up, tie beef in 4 places with thread. With sharp knife, cut roll into 4 equal pieces.
Place rolls, cut side up, on broiler pan. Broil 4 to 6 inches from heat for 12 to 16 minutes or until beef is of desired doneness, turning once.