3 1/2 lb boneless round rump roast or sirloin tip roast, trimmed
2 tablespoons Dijon mustard
1 tablespoon lemon juice
2 teaspoons coarse ground black pepper
1/2 teaspoon ground cloves
1/2 teaspoon dried oregano

SAUCE:
8 ounces sour cream
1 tablespoon Dijon mustard
1 teaspoon lemon juice
1 teaspoon prepared horseradish

Place roast in a large bowl. In a small bowl, combine the mustard, lemon juice, pepper, cloves and oregano; rub over roast. Cover and refrigerate overnight. Grill roast, covered, over indirect medium heat for 2 hours or until roast reaches desired doneness (for rare, a meat thermometer should read 140¼F, medium, 160¼F, well-done, 170¼F). In a small bowl, combine the horseradish sauce ingredients. Serve with beef.