Combine vinegar and seasonings, stir well.
Add honey and oil, stirring until blended.
Remove 1/3 cup marinade; set aside for preparing couscous.
Slice steak diagonally into thin slices.
Place steak in marinade, turning to coat.
Marinate in the refrigerator for 1 hour or up to overnight.
Remove steak from marinade, discarding marinade.
Cook steak in a skillet over medium heat for 8-10 minutes, or until browned.
Turn steak, cover, and reduce heat to low. Cook 7-10 minutes for medium doneness.
While steak is cooking, prepare couscous. In a large saucepan, combine water, reserved marinade, garbanzo beans, tomatoes, and parsley.
Bring to a boil over high heat.
Stir in couscous, cover, and remove from heat.
Let stand for 5 minutes, then fluff with a fork and serve with steak.