The 23-year-old Californian set the tone early with a flying lap of 1m07.5382s around the 11-turn, 2.238-mile natural terrain road course.
His fastest time was achieved on a set of the harder primary tyre compound.
Behind the Andretti Autosport pacesetter and two-time Laguna Seca race winner was Arrow McLaren’s Pato O’Ward, who trailed by 0.0529s, and was ahead of team-mate Alexander Rossi in third. O’Ward logged 33 laps, the most in the session.
Marcus Ericsson’s final race weekend with Chip Ganassi Racing saw him fourth on the leaderboard, 0.2531s off the top spot. Andretti’s Kyle Kirkwood finished up fifth.
Rahal Letterman Lanigan Racing was represented in sixth and seventh, led by rookie Juri Vips ahead of team-mate Graham Rahal. Juncos Hollinger Racing was represented in the top 10 with Callum Ilott in eighth.
Six-time IndyCar Series champion Scott Dixon came away ninth, with Ed Carpenter Racing’s Rinus Veekay rounding out the rest of the top 10.
Source: Autosport