Preheat oven to 425 degree F. Starting on a long side, split tenderloin horizontally, almost to opposite side. Coat cut sides with garlic and the 2 tablespoons fresh or 2 teaspoons dried sage. Fold cut sides together; place meat in a 13x9x2-inch baking pan. Place onions around the meat. Layer the sweet peppers on top of the onions.
Drain pears, reserving syrup. Slice pears; add to vegetables in pan. Pour vinegar over all. Roast, uncovered, about 35 minutes or until an instant-read thermometer registers 160 degree F.
Meanwhile, add water to reserved syrup to equal 2 cups. In a medium saucepan combine syrup mixture, barley, the 2 teaspoon fresh or 1/2 teaspoon dried sage, and salt. Bring to boiling; reduce heat. Simmer, covered, for 10 to 12 minutes or until barley is tender and most of the liquid is absorbed. Spread barley on a serving platter. Slice meat; arrange on barley. Using a slotted spoon, transfer vegetables and pears to platter around meat. Serve with pan juices. Makes 4 to 6 servings.