The Milwaukee Brewers complete a stunning season-opening, three-game sweep of the Baltimore Orioles by scores of 11 – 3, 16 – 3, and 13 – 5. Sixto Lezcano, Gorman Thomas, and Cecil Cooper provided the Brewers with a grand slam in each game to set a major league record.

This Day In Baseball

On April 9, 1978 — The Milwaukee Brewers complete a stunning season-opening, three-game sweep of the Baltimore Orioles by scores of 11 – 3, 16 – 3, and 13 – 5. Sixto Lezcano, Gorman Thomas, and Cecil Cooper provided the Brewers with a grand slam in each game to set a major league record.

Source
Baseball Reference April 9