This recipe assumes that you will be buying a whole, untrimmed beef tenderloin. Even though you will trim the beef yourself, there will still be a fair amount of waste: A whole tenderloin weighing 6 pounds trims down to about 3 1/2 pounds, plus about 3/4 pound of meat culled from the trimmings to put to another use. Or, you can buy a 3 1/2 to 4-pound trimmed tenderloin.

Marinated Beef Tenderloin

1 (6 pound) beef tenderloin, untrimmed
Marinade:
1 cup hearty red wine, such as Zinfandel
Grated zest and juice of 1 large orange
1/3 cup soy sauce
1/3 cup extra virgin olive oil
1/4 cup balsamic vinegar
2 garlic cloves, crushed under a knife
1 1/2 teaspoons dried rosemary
1 1/2 teaspoons dried thyme
1/2 teaspoon whole black peppercorns
1 tablespoon extra virgin olive oil
1/2 teaspoon salt
1/2 teaspoon freshly milled black pepper

Drain the beef, rinse under cold running water and pat dry with paper towels. Using a sharp, thin bladed knife, trim away any fat, including the large lump at the wide end, and discard. Pull and cut away the long, thin "chain" muscle that runs the length of the tenderloin. (If you wish, trim away the fat from the chain and reserve the meat for another use.) Following the natural muscle separation, cut away the large clod of meat at the wide end and reserve for another use. At one end of the meat, make an incision under the silver sinew covering the meat. Slip the knife under the sinew and pull and trim it away. Work lengthwise down the tenderloin until it is completely free of sinew and fat.
Fold the thin ends of the meat underneath so the tenderloin is the same thickness throughout its length, and tie with kitchen string. Tie the roast crosswise at 2 to 3-inch intervals.
To make the marinade, whisk all the ingredients in a large bowl to combine. Immerse the tenderloin in the marinade. Cover and refrigerate, turning occasionally, for at least 2 hours and up to 4 hours. Drain the tenderloin and let stand at room temperature for 1 hour before roasting.
Position a rack in the center of the oven and preheat to 425°F (220°C). Rub the tenderloin with the oil, and season with the salt and pepper. Place in a large roasting pan (no need to use a roasting rack.) Roast until an instant-read thermometer inserted in the center of the roast reads 120°F to 125°F (50°C)for medium-rare meat (the internal temperature of the meat will continue to rise about 10°F outside of the oven), about 35 minutes.
If serving hot, let stand for 10 to 15 minutes before carving. For a buffet, cool for at least 30 minutes, then carve and serve within 2 hours. Or cool completely, wrap tightly in foil, and refrigerate for up to 2 days before carving and serving at room temperature.

Makes 8 to 12 main-course servings, and 16 to 20 buffet servings.