Whisk together oil, soy sauce, vinegar, lemon juice, Worcestershire sauce, Dijon mustard, garlic, and pepper for marinade until thoroughly combined. Place steak in a large ziplock bag.

Pour marinade over flank steak in the ziplock bag; turn several times to coat thoroughly with marinade. Cover, and refrigerate for 2 to 6 hours, or up to 12 hours if you have time.

Cook steak on the preheated grill for about 5 minutes per side, or to desired doneness.