After an off-year in 1976, the Red Sox had an opportunity to reacquire two players from the Milwaukee Brewers: Bernie Carbo and George Scott. Carbo was great for the Sox in 1975 and George Scott was a star player for the Sox from 1966-1971. While Carbo and Scott would be great for the Red Sox in 1977, their careers would quickly go south after that.
Cooper, on the other hand, would go on to post very good numbers in Milwaukee for 11 seasons. It was a trade that the Red Sox would come to regret in the long-term, as the Brewers had the consistent stalwart at first base that the Red Sox would lack for many years.
This trade of Cooper for Scott and Carbo would end up being almost as bad as the trade that sent George Scott to Milwaukee in the first place. The prize in that deal for the Red Sox was speedy outfielder Tommy Harper, who would have one great season for Boston in between two not so great ones. The Brewers got one great year of pitcher Jim Lonborg out of that deal and 5 of Scott's best career seasons.
In hindsight, the Red Sox should have kept Cecil Cooper. But considering they were selling low, at the time, it probably didn't look so bad. Still, it’s one in a long line of trades that went bad for the Sox, which contributed to their World Series title draught for so long.