On March 21, 2019, Kaulig Racing announced Allmendinger would join the team's No.
10 car for a part-time Xfinity Series schedule.
His schedule was originally a four-race slate beginning in July at Daytona, followed by the road course events at Mid-Ohio, Road America, and the Charlotte Motor Speedway Roval.
In the 2019 Circle K Firecracker 250 at Daytona, Allmendinger finished third, but was disqualified and relegated to last place after his car failed an engine vacuum test during post-race inspection.

On July 17, Kaulig announced that Allmendinger would add a fifth race to his schedule: the 2019 Zippo 200 at The Glen at Watkins Glen International on August 3, 2019.
He was once again disqualified when his second-place finishing car was discovered to be too low on both rear corners during post-race inspection.

At his final start of the year at the Charlotte Roval, he picked up his first win of the season and third of his Xfinity Series career, beating out RCR driver Tyler Reddick.

A few weeks after his Roval win, Kaulig president Chris Rice stated in an interview that Allmendinger would tentatively return to the team to drive for them in all of the Xfinity Series road course races again.
In addition to those four races, he added he could likely run the new race for the series at Martinsville, a track that Allmendinger has historically performed well at over the course of his NASCAR career.
Allmendinger formally moved to the No.
16, Kaulig's part-time third car, for 2020 because the No.
10 was taken over full-time by Ross Chastain.
On January 30, 2020, Kaulig Racing announced Allmendinger would appear in eight races for the team, predominantly at the road courses and superspeedways.
Further races at Bristol and Atlanta were later added to his schedule, the latter in which he scored his first career victory on an oval.

The Atlanta victory made Allmendinger eligible for the series' $100,000 Dash 4 Cash bonus available the following week at Homestead-Miami.
Kaulig added the race to Allmendinger's schedule, where he finished fourth, enough to claim the bonus.

At the Cup Series race at Martinsville in June, Allmendinger was on standby for RCR's Austin Dillon, who was expecting his first child with his wife, Whitney.
Allmendinger continued acting on standby until Homestead-Miami, but was not needed as Dillon's son was born Sunday morning before the Homestead race.

In August, Allmendinger finished second at Road America to Team Penske's Austin Cindric.
At the Daytona road course race, Allmendinger finished fourth but was involved in controversy as he spun Justin Allgaier in the closing laps, leading to a confrontation between the two drivers.
On March 21, 2019, Kaulig Racing announced Allmendinger would join the team's No. 10 car for a part-time Xfinity Series schedule. His schedule was originally a four-race slate beginning in July at Daytona, followed by the road course events at Mid-Ohio, Road America, and the Charlotte Motor Speedway Roval. In the 2019 Circle K Firecracker 250 at Daytona, Allmendinger finished third, but was disqualified and relegated to last place after his car failed an engine vacuum test during post-race inspection.
On July 17, Kaulig announced that Allmendinger would add a fifth race to his schedule: the 2019 Zippo 200 at The Glen at Watkins Glen International on August 3, 2019. He was once again disqualified when his second-place finishing car was discovered to be too low on both rear corners during post-race inspection.
At his final start of the year at the Charlotte Roval, he picked up his first win of the season and third of his Xfinity Series career, beating out RCR driver Tyler Reddick.
A few weeks after his Roval win, Kaulig president Chris Rice stated in an interview that Allmendinger would tentatively return to the team to drive for them in all of the Xfinity Series road course races again. In addition to those four races, he added he could likely run the new race for the series at Martinsville, a track that Allmendinger has historically performed well at over the course of his NASCAR career. Allmendinger formally moved to the No. 16, Kaulig's part-time third car, for 2020 because the No. 10 was taken over full-time by Ross Chastain. On January 30, 2020, Kaulig Racing announced Allmendinger would appear in eight races for the team, predominantly at the road courses and superspeedways. Further races at Bristol and Atlanta were later added to his schedule, the latter in which he scored his first career victory on an oval. 
The Atlanta victory made Allmendinger eligible for the series' $100,000 Dash 4 Cash bonus available the following week at Homestead-Miami. Kaulig added the race to Allmendinger's schedule, where he finished fourth, enough to claim the bonus.
At the Cup Series race at Martinsville in June, Allmendinger was on standby for RCR's Austin Dillon, who was expecting his first child with his wife, Whitney. Allmendinger continued acting on standby until Homestead-Miami, but was not needed as Dillon's son was born Sunday morning before the Homestead race.
In August, Allmendinger finished second at Road America to Team Penske's Austin Cindric. At the Daytona road course race, Allmendinger finished fourth but was involved in controversy as he spun Justin Allgaier in the closing laps, leading to a confrontation between the two drivers.
A. J. Allmendinger