EXCLUSIVE : NBC ’s three Chicago series will have their leads in place when they return in the fall as Chicago Med ‘s S. Epatha Merkerson and Oliver Platt , Chicago Fire ‘ s Taylor Kinney and Miranda Rae Mayo as well as Chicago P.D. ’s Jason Beghe are all locked in to continue on their shows. Med’ s Merkerson and Platt and Fire‘s Kinney and Mayo have signed new deals to continue on their shows, sources said. Like last year, negotiations with the quartet started after the three Chicago series, produced by Wolf Entertainment and Universal Television, were renewed for next season. (The pickup came in early this time, in March). Also like last year, Kinney was the last of the group to close a new pact. Beghe will return to P.D. under his current contract. As Deadline reported last year , he has more time on his existing deal. Watch on Deadline Kinney, Beghe, Merkerson and Platt have been headlining their Chicago series as original cast members from Day 1.…