Drizzle the tri-tip with the red wine vinegar. Rub the tri-tip with the garlic, olive oil, salt, and black pepper. Sprinkle with oregano, then add the red pepper to the fatty side of the tri-tip. Let stand 24 hours or more.
Heat coals and prepare grill. Pile coals along one side of the grill, and place tri-tip opposite. Cook over indiret heat for 45 minutes (rare) to 75 minutes (medium) -- use a meat themometer if you're uncertain, or cut the tri-tip in half.