On April 21, 1970, Flynn Robinson and Charlie Paulk were dealt to the Cincinnati Royals. In exchange, the Bucks received Oscar Robertson, an All-Star in each of his 10 seasons in Cincinnati, who still had plenty of fuel left in his tank at the age of 31.
The player to whom other great "all-around" players are compared, Robertson joined Kareem Abdul-Jabbar to immediately form one of the most formidable inside-outside duos in NBA history. The NBA's first "big" point guard at 6-5, Robertson averaged 19.4 ppg, 5.7 rpg and 8.2 apg in his first season in Milwaukee, exhibiting the versatility that led to nine All-NBA First Teams in Cincinnati.
The Bucks won 66 games and advanced to the NBA Finals against Baltimore. For only the second time in NBA history, the Finals ended in a 4-0 sweep, and The Big O finally had the NBA championship that had eluded him in Cincinnati. Robertson averaged 18.3 ppg in Milwaukee's 12-2 postseason.
Robertson played three more seasons with the Bucks, and the team never won fewer than 59 games. In 1973-74, the last of his 14 NBA seasons, Oscar again led the Bucks to the Finals. In a memorable seven-game series against the Boston Celtics, the Bucks came up one game short.
Robertson retired after having led Milwaukee to a 248-80 record in four seasons. Robertson, the only Buck to wear the No. 1, had his jersey retired on October 18, 1974.
Milwaukee Totals: 71-74 (Four seasons)
| G | Min. | FGM-A | .PCT | FTM-A | PCT | REB | AST | PF | PTS | AVG |
| Career | 288 | 10798 | 1845-3835 | 0.481 | 1111-1318 | 0.843 | 1424 | 2156 | 618 | 4701 | 16.3 |
| Playoffs | 47 | 1845 | 297-646 | 0.460 | 157-191 | 0.822 | 216 | 401 | 135 | 751 | 16.0 |