Coming in late on this one but thought I would add cuz its really good and easy for a Flank steak

Score x crossed top & bottom of steak ...if you have a super sharp knife be careful to not cut too deep...just about 1/4 inch or less each side
Put steak in tupperware container.....
On top of steak place:
garlic...whatever you have on hand...powder, chopped
1 med white or yellow onion sliced (like for fajita's)
(I also add a green onion for that flavor)
1 green pepper cut in strips...I sometimes add red too if I have it

Generously douse w/ Teriyaki sauce
Sprinkle lightly with Montreal steak seasoning
Cover tightly and turn container over every now and than. I usually let it sit over night or all day.
Cook on super hot grill only about 5 mins per side....slice on angle thinly.

The flavor of the veggies soaks into the meat. You can cook the veggies on top of the meat or I put in a corning-ware dish (spray with Pam) and put the dish on the grill...stir every now and than