Route 27 crosses into Rahway, Union County and intersects the northern terminus of Route 35. Route 27 continues north using four-lane St. Georges Avenue. The route passes through Rahway, passing by residences and businesses. In Rahway, the route sees about 25,022 cars a day. It continues northeast, intersecting multiple county routes, such as County Route 602 (West Inman Avenue), County Route 621 (Hazelwood Avenue), County Route 608 (Milton Street), and County Route 613 (Westfield Avenue/West Grand Avenue). The route crosses into Linden when passing Stuart Place, where the route heads through a more commercial setting with businesses lining both sides of the road. In Linden, the road intersects County Route 615 (North Stiles Street). At the intersection with County Route 617 (Wood Avenue), Route 27 forms the border of Roselle to the west and Linden to the east, with about 23,081 vehicles using the road on a daily basis The route crosses the inactive Rahway Valley Railroad line that is owned by the Staten Island Railway. It passes by Warinaco Park and forms the border between Elizabeth to the west and Linden to the east before entirely entering Elizabeth at the Richford Terrace intersection.