Tampa Bay has the best record in the NHL's Eastern Conference at 12-5-0 but three of those losses have come in the Lightning's three games against Boston. It was the second time in those three games Tampa Bay was shut out and the Lightning had just one goal in the other loss.
Boston ran its home ice winning streak versus Tampa Bay to eight games.
Rask picked up his second shutout of the season with 28 saves, including 11 in the second period and 10 in the third.
Boston's first two goals came in a 20-second spurt late in the second period, two of the Bruins' six shots on goal in the period. Patrice Bergeron wristed in a shot off a pass from Louis Eriksson at the 17:09 mark and a shot by Daniel Paille was deflected past Tampa Bay goaltender Anders Lindback at 17:29.
The Bruins made it 3-0 in the final minute when Jarome Iginla scored on a backhand shot.
Bergeron has six goals this season. The goal by Paille was his second and Iginla has four.