Heat oven to 425°F. Combine onions, Brussels sprouts, oil and 1 teaspoon salt on metal baking pan; toss to coat. Set aside.
Combine thyme and pepper in small bowl. Reserve 1 teaspoon thyme mixture for sauce; set aside. Press remaining thyme mixture evenly onto all surfaces of beef Tenderloin Roast.
Place roast on rack in shallow roasting pan. Insert ovenproof-meat thermometer so tip is centered in thickest part of beef. Do not add water or cover. Place prepared vegetables in oven with roast. Roast beef in 425°F oven 35 to 45 minutes for medium rare; 45 to 50 minutes for medium doneness. Roast vegetables 45 to 50 minutes or until tender and lightly browned
Meanwhile, prepare sauce. Combine vinegar and shallots in small saucepan; bring to a boil. Reduce heat; simmer 3 minutes. Stir in cranberry sauce; bring to a boil. Reduce heat; simmer 6 minutes to blend flavors, stirring occasionally. Remove from heat; stir in reserved 1 teaspoon thyme mixture and remaining 1/4 teaspoon salt. Keep warm.
Remove roast when meat thermometer registers 135°F for medium rare; 145°F for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand 15 to 20 minutes. (Temperature will continue to rise about 10° to 15°F to reach 145°F for medium rare; 160°F for medium.)
Carve roast into slices; serve with vegetables and sauce.