1/3 cup oil (any oil will do-canola, olive, grapeseed)
1 cup Teriyaki sauce
1 onion, sliced
1 (2") piece of ginger, peeled and cut into chunks
2 garlic cloves, mashed (no need to minced)
Place all ingredients in a zip lock or bowl and let marinate in refrigerator. This can go for as long as two to three days or for as little as 30 minutes. But obviously the longer it marinates the stronger the flavor.
When ready to cook bring the meat out of the refrigerator and let come to room temperature to ensure even cooking. This should take about 15-20 minutes.
Heat the grill to medium high heat. Discard the marinade.
Grill for about 8 minutes a side for medium rare (140° by an instant read thermometer). You want it to be a medium rare since flank steak is a tough cut of meat. But you may cook it like my husband did, but just get ready to chew:)
Once the meat is at 140° remove from the grill to a plate and cover tightly with foil. Let it rest for about 10 minutes.
When ready to serve, slice it thinly against the grain.