Marinate the steak by whisking together the steak marinade; water, olive oil, lime juice and taco seasoning. Place flank steak in a resealable plastic bag, or dish with tight fitting cover. Pour marinade over meat. Marinate for at least 2 hours, or for up to 24 hours.
Preheat your gas or charcoal grill to medium high heat.
Skewer mini peppers and quartered onions. Brush lightly with olive oil and top with salt and pepper to taste.
Place steak and vegetable skewers on hot grill. Cook steak for 6-8 minutes per side for a medium-rare doneness. Approximately 10 minutes per side for medium. Internal temperature of steak should read 130-135 degrees. Continually turn vegetables until all sides are lightly charred.
Remove steak from grill and let rest 10 minutes before slicing. While meat is resting, slice vegetables for serving.
If desired, lightly grill tortillas for a slight char, approximate 1 minute per side.
Serve with loaded guacamole and southwestern corn salsa.