In a bowl, mix together the olive oil, lemon peel, thyme, marjoram, salt and pepper. Rub the beef tenderloin with the mixture and set aside. Combine the remaining oil mixture with the vegetables and place them in the bottom of the crock pot. Place the beef on top of the vegetables. Cover the crock pot and cook on low heat for 4-5 hours or until the beef is tender and cooked through. Remove the beef from the crock pot and place on a cutting board. Let rest, covered, for 5 minutes. Slice the beef and serve with the seasoned vegetables.