In a large saucepan combine half of the beer and the crushed red pepper; bring to boiling. Add sausage and Brussels sprouts. Return to a simmer, cover and cook 5 to 8 minutes or until sprouts are tender. Drain and set aside.
Meanwhile, in a large skillet melt 1 tablespoon butter; add apples. Cook, turning occasionally, until apples are just tender. Transfer to a platter.
Add sausage and Brussels sprouts to skillet. Cook, turning occasionally, until browned. Add to platter; cover. Drain fat from skillet.
Carefully add remaining beer to skillet (mixture may foam); stir to scrape up browned bits. Add remaining 1 tablespoon butter, brown sugar, cider vinegar, and orange peel. Bring to boiling; reduce heat and boil gently, uncovered, 5 to 6 minutes or until slightly thickened. Return sausage, Brussels sprouts, and apples to skillet to coat in glaze. Return to serving platter. Sprinkle with sage.