Nope... that was Jean Shepherd, who wrote the screenplay and provided the narration for 'A Christmas Story'. Shepherd also has a cameo appearance in the department store scene, as the man who directs Ralphie and Randy to the end of the line.
The narrator for 'Underdog' was an actor named George S Irving. One of his most famous off-Broadway roles was a voice-over for 'The Year Without a Santa Claus', in which he played the embittered Heat Miser opposite Dick Shawn's Snow Miser. He did another voice-over as Gepetto in 'Pinocchio's Christmas', and also appeared in television commercials for White Owl cigars.