Chastain had taken the lead on the final restart, with two laps of overtime ahead, but Briscoe passed him in Turn 2 and held on for nearly two more laps for the win.
Chastain finished second for the second straight race and also won the final $100,000 Dash 4 Cash bonus. It was his second Dash win in two races.
Briscoe is No. 1 in the standings, holding a three-point edge over Noah Gragson.