The 10-colour long perfector joins another 10-colour plus an eight-colour XL 105 at the 240-staff, Merthyr Tydfil-based business.
The XL 105 battery, which was installed on 1 April, is expected to burn through around 60m impressions each year.
Managing director Andrew Jones said its recent kit investment would enable it to achieve "higher productivity and faster makereadies", allowing it to compete in a "tough marketplace".
The new addition includes CutStar reel-to-sheet technology, plus Inpress Control spectral measurement and automatic inline colour and register adjustment.
It also features the simultaneous plate-changing Autoplate XL device to decrease makeready times, which Jones described as "critical".
"Magazines have declined and some publishers have reduced runs," he said, adding "We have won work from web producers in recent months."
The colour control features have also carved new efficiencies for the £20m-turnover company.
"The colour predictability of running closed-loop colour, and to ISO 12647 standards using Inpress Control, means that one major publisher had decided not to do on-press passes any longer because it knows our colour is predictable and provable," said Jones.
In addition to the press investments, the company has also added two Stahlfolder TH 82s to improve its folding capacity.
The final XL 105 completes Stephens & George's £8m two-year reinvestment plan. The publisher is now using 28 B1 XL units, five B2 XL units and eight B2 SM units.
