Combine beef stew mix with water and stir to combine.
Place onions in bottom of slow cooker. Add meat strips and pour over seasoning water.
Add soy sauce.
Cook for half the time, on low for 4 hours or high for 2 hours.
Add peppers and continue to cook for remaining time, 4 hours on low or 2 hours on high. Serve over rice or noodles. Sprinkle with sesame seeds before serving.