The Middelborough/Lakeview Line is the most successful of the three Old Colony Lines that saw commuter rail service discontinued in 1959. Service along the mainline of these 3 branches was originally replaced by the South Shore Branch of the Red Line in 1971 as far south of Braintree. In the early 1980s limited service operated between Braintree and Cape Cod over today's Middleborough/Lakeview Line (which the Cape Cod Flyer operates over the entirety of today) but this wasn't sustainable.

Finally on September 26, 1997 service was restored to the Middleborough/Lakeville Line with the building of six new ADA accessible high-platform stations on the portion of the line south of Braintree. The line is single tracked with long sections of double-tracked passing sidings. The line's reopening required the rebuilding of a regular FRA-compliant train track (portions are still single-track) along the Red Line's ROW to restore service to South Station from the Old Colony Lines, whose tracks had seen continuous freight service since passenger service ended in 1959.

The tracks were heavily rehabilitated as a 59 mph passenger railroad. The rehabilitated railroad received what turned out to be defective concrete ties, requiring the conversion back to traditional timber railroad ties from 2010 through 2012 that included the replacement of off peak train service with buses and no weekend service.

In 2020 new Regional Rail-style timetables debuted on the Middleborough/Lakeville Line with service roughly every 75 minutes throughout the day on weekdays and service every 90 minutes on weekends.