Somerset opener Nick Compton responded to his England omission with an innings of 81 against Australia before the tourists fought back on day one.
Chris Jones top-scored with a career-best 130 but his departure sparked a collapse, the county going from 304-3 to 320 all out at Taunton. Australia survived the one-and-only over they had to face to close on 2-0.
While Jones impressed with a maiden first-class century from number three in the order, most of the spotlight will fall on Compton's knock.
The right-hander seems to have lost his place as Alastair Cook's partner at the top of the order for the Ashes after being overlooked for England's warm-up fixture against Essex.
He was instead free to take part in Somerset's four-day affair against Australia, who were playing for the first time since Darren Lehmann replaced Mickey Arthur as coach.
The visitors also welcomed back skipper Michael Clarke after a back injury for the first of their two warm-up matches before the opening Test of the series at Trent Bridge gets underway on July 10.
Having won the toss and chosen to bat first, Marcus Trescothick fell in the fourth over to left-arm seamer Mitchell Starc's bowling for seven.
However Compton - who managed just 39 runs in the two Tests against New Zealand on home soil earlier this year - took the chance to give the national selectors a reminder of his abilities during a second-wicket stand of 170.
He had struck 13 fours in his patient 144-ball innings by the time he fell to Nathan Lyon's off-spin, leaving Somerset on 185-2.
Jones, only playing because of an injury to South African Alviro Petersen, then combined with James Hildreth to put on a further 119 before becoming the solitary victim in the innings for James Faulkner (1-70).
His departure, along with the second new ball being taken, then sparked an amazing turnaround in proceedings in front of a crowd of around 7,000.
Starc and James Pattinson both ran riot as Somerset at one stage lost six wickets without the addition of a run, the latter getting Hildreth leg before for 66 on his way to taking 4-56.
Left-armer Starc wrapped up the innings by getting last-man George Dockrell lbw with the first delivery of his 17th over, giving him fine figures of 4-33.