The 40-year-old former England opener made an unbeaten 158 - his 57th first-class century - out of a total of 305 before Gloucestershire closed on 52 for 2. Walsh took 5 for 88.
Mark Ramprakash, ignored by England for the one-day series, made 83 for Middlesex against Hampshire at Southampton. He and Mike Gatting put on 139 in 46 overs for the third wicket as the county champions reached 280 for 8 from 110 overs.
Yorkshire were in the runs at Headingley, with Craig White, dropped three times, hitting an unbeaten century to help his side to 300 for 8.
Mark Taylor was appointed captain of Australia yesterday, succeeding Allan Border who retired earlier this month after 10 years in charge. The 29-year-old opener, who has been Border's deputy for the past two years, will have wicketkeeper Ian Healy as vice-captain for the forthcoming tour of Sri Lanka and Pakistan.Reuse content