Whether tailgating or grilling at home, tri-tip roast or steak might have your guests raving and asking, "What is this?"

That's what happens when Ron Krantz cooks a tri-tip roast, which is the triangular cut of beef on the bottom sirloin, long popular out West and making its way onto Midwestern platters in recent years.

Considered a lower-fat cut of beef, it has internal fat that makes it tender.

"It just puffs right up," said Krantz, executive vice president of the privately owned UW Provision Co., 2315 Pleasant View Road, Middleton. A 2-inch-thick cut increases to 3 inches as it cooks, he said.

"It's so tender and flavorful," he said. "The juices just flow out of them. It's unbelievable."

When shopping for tri tip, he said, "Look for marbling." Regarding the outside fat, he suggested trimming it moderately. "An eighth-inch layer of fat outside is good for grilling."

He marinates the meat with teriyaki or sweet-and-sour sauce or rubs on steak seasoning at least an hour before grilling. "Longer is better," he said, adding that he sometimes does this the night before then takes the meat out of the refrigerator to bring it back to room temperature before grilling.

Charcoal briquettes lend an unwelcome flavor, so he buys natural lump charcoal for grilling in his Green Egg, which has a temperature-control feature. He heats it for 15 to 20 minutes, then cooks the tri tip at 300 to 325 for about 20 minutes on each side for medium rare or rare. UW Provision's cash-and-carry store used to sell only 20-pound boxes of tri-tip roasts but now packages a 2- to 3-pound roast for $3.29.

Grocery stores — including Sentry at Hilldale, Trader Joe's on Monroe Street and Copps in Shorewood Hills — sell the cut for about $5.50 to $6 per pound; Whole Foods on University Avenue usually carries "all-natural" tri tip for $9.99 per pound; and Artamos Meats on South Whitney Way near Odana Road sells certified organic tri-tip roast from beef raised and processed in southern Wisconsin for $11.99 per pound.

Copps offers the cut on request, so customers are advised to call a day ahead, said Shorewood Hills meat manager John Rikli.

He and Lars Gould, a chef for Copps, described how they like to prepare tri-tip roast. They start by coating both sides with olive oil and coarse kosher salt — adding pepper or any other seasoning desired — and letting it stand at room temperature for a half hour before grilling. They sear the meat with direct heat until somewhat crusty on the outside, then wrap it in foil and finish it on indirect heat. Both advocate using a meat thermometer to check for doneness, which would be 145 degrees in the middle for medium rare.

Whole Foods' Web site notes that the triangular shape solves the problem of cooking for guests with differing preferences for doneness, since one end of a 1 1/2- to 2 1/2-pound roast could be medium well and the other medium rare. The company also offers the following recipe online.

Grilled Tri-Tip Roast

1 (1 1/2 to 2 pound) beef tri-tip roast

1 package steak spice rub

Charcoal

Coat all sides of the roast with the spice rub. Place on a plate, cover and refrigerate for 2 hours. Get your coals started (we like a chimney starter) and when hot, move them to one side of the grill. Place the roast on the other side, not directly over the coals. Close the top of the grill and close all vents halfway to maintain a constant low heat. Check every 15 minutes and add charcoal if necessary, turning roast over once during cooking. Slow cook for about an hour, or until desired doneness. Let rest for 5 to 10 minutes, then slice against the grain into 1/4-inch thick slices and serve. Serves 4 to 6.

Per serving (about 5 ounces): 220 calories (100 from fat), 11 g total fat, 4 g saturated fat, 27 g protein, 0 g carbohydrate, 85 mg cholesterol, 260 mg sodium.