Notre Dame. No surprise. OU is 2-9 All Time against ND.
FWIW, OU played but 16 teams with a winning record during that 47 game streak. Including the two Bowl opponents. Only 3 of the 16 won more than 7 games. The two 10-1 Maryland teams faced in Orange Bowl games and 8-2-1 Colorado in 1956. Which was the ONLY team with a winning record that OU faced in 1956. The 1957 ND team that ended the streak was 7-3 on the season, and was coming off a 6-20 loss to Navy and a 6-34 loss at Michigan State the two previous weeks.