Soak skewers in water for 30 minutes before using.
Place pork cubes in resealable plastic bag; add salad dressing, red pepper flakes and fennel seed. Seal bag; refrigerate for at least 1 hour to overnight to marinate pork.
When ready to cook, thread pork, peppers and onion on skewers. Discard marinade. Place kabobs on greased broiler pan and broil 5 inches from heat, or grill over medium-hot coals, for about 5 minutes per side.