Notes: Brush some of the marinade on bell peppers and onions; grill them next to the meat for about 15 minutes. (Stop brushing on marinade at least 5 minutes before veggies are done, so heat can kill any bacteria from meat.) Prep and cook time: about 35 minutes, plus at least 2 hours to marinate.
In a gallon-size zip-lock plastic bag, combine Shiraz, soy sauce, oil, vinegar, lemon juice, Worcestershire, mustard, and garlic. Add tri-tip and seal bag. Chill at least 2 hours or up to 1 day, turning occasionally.
Lightly oil a barbecue grill over a solid bed of medium coals or medium heat on a gas grill (you can hold your hand at grill level only 4 to 5 seconds). Lift tri-tip from marinade and lay on hot grill; discard marinade. Close lid on gas grill. Cook tri-tip, turning every 5 minutes, until rare in center of thickest part (still pink; cut to test), 125° to 130° on a thermometer, about 25 minutes, or until as done as you like.
Let meat rest 5 minutes, then cut across the grain into thin, slanting slices.
Wine: A fruity Shiraz or Syrah (the same grape) with a hint of sweet pipe-tobacco smoke.