Alex Palou topped final practice at the Children's of Alabama Indy Grand Prix with a staggering margin to the chasing pack.
Compared to the first session, which was interrupted by three red flags, Saturday's practice was a far more straightforward affair with drivers piling in the laps.
McLaughlin continued where he had left off and spent the opening 30 minutes of the 45-minute session at the top of the times, steadily lowering the benchmark.
With 16 minutes remaining, however, Palou climbed ahead of his rival with what transpired to be his best time of the morning.
Although the session lacked the drama of first practice, it was not without incident.
Just as he had on Friday, McLaughlin pushed the limits of his suspension with a dramatic leap over the Turn 9 kerbs.
Pato O'Ward and Colton Herta also survived hairy moments at Turns 1 and 2, with both drivers losing the rear end of their respective cars but holding the slide in a pair of moments that are sure to make their career highlights reels.
O'Ward's luck held late in the session as he mimicked McLaughlin's earlier kerb-hopping at Turn 9.
A.J. Foyt Enterprises rookie Benjamin Pedersen was less fortunate as he failed to gather his car at the same corner and endured a trip across the gravel.
Drivers are guaranteed 45 minutes of running in the session, regardless of red flags, so when a spin from Helio Castroneves caused a brief interruption with 46 seconds remaining, the field was granted an additional lap, although it had no effect on the standings.
Qualifying will get underway at 15:00 ET (05:00 AEST).