Coors Light knocked Budweiser off its perch to become the second best-selling beer by volume in the U.S. last year, according to Beer Marketer's Insights.

The new No. 2 brew ended the year 2011 with sales of 18.23 million barrels, a 0.8% gain. Budweiser slipped 4.6% to 17.7 million barrels.

Coors Light is made and marketed by MilerCoors,...