Slow-Cooked Sirloin

1 boneless beef sirloin steak (1- 1 1/2 lbs.)
1 medium onion, cut into 1-inch chunks
1 medium green pepper, cut into 1- inch chunks
1 (14 1/2 oz) reduced-sodium beef broth
1/4 c. Worchetershire sauce
1/4 tsp. dill weed
1/4 tsp. dried thyme
1/4 tsp. pepper
Dash crushed red pepper flakes
2 Tbsp. cornstarch
2 Tbsp. water

In a large nonstick skillet coated with cooking spray, brown beef on both sides. Place onion and green pepper in a 3 qt slow cooker. Top with beef. Combine the broth, Worcestershire sauce, dill, thyme, pepper and pepper flakes; pour over beef. Cover and cook on HIGH for 3-4 hours or until meat reaches desired doneness and vegetables are crisp-tender. Remove beef and keep warm. Combine cornstarch and water until smooth; gradually stir into cooking juices. Cover and cook about 30 minutes longer or until slightly thickened. Return beef to the slow cooker; heat through.