Surrey 200 and 135 for 4 (Burns 63) lead Hampshire 290 (Berg 80, Holland 51, Bailey 51, T Curran 4-69) by 45 runs
Rory Burns continued his eye-catching record against Hampshire by scoring 63 as Surrey battled from a first innings deficit to lead by 45 at the Ageas Bowl.
Ahead of this fixture, Burns averaged 125.20 against the southern county in his previous six appearances against them.
That had been boosted by an epic unbeaten 219 earlier of the season at the Kia Oval, in which he was on the pitch for all but 29 minutes of the match, along with a pair of centuries in the two meetings last season.
And he looked in top form again as he doggedly batted Surrey away from major danger under grey skies and a slow pitch.
He brought up his 34th first class half century by rocking onto his back foot and pulling part-time spinner Joe Weatherley to the boundary - his 133 delivery faced.
The runs were much needed for Surrey as he lost opening partner, and first innings top scorer, Ryan Patel after putting on 44, the teenager gloving a sweep to first slip Sean Ervine who moved to leg slip to complete the catch.
Burns also watched from the other end as Scott Borthwick and Jason Roy completed dismal matches with the bat - the pair scoring ducks in the first innings and 1 apiece in the second.
Borthwick was a tad unlucky as Liam Dawson's delivery kept low before ricocheting behind to a smart catch by Tom Alsop behind the stumps, while Roy was clean bowled by Kyle Abbott.
Burns continued his steady innings with Ben Foakes, the pair putting on 71 and putting Surrey into the red, before he became Weatherley's maiden first-class wicket when he was leg before.
Foakes manoeuvred his way to 33 not out at the close, with his side leading by 45 runs although with rain due on the fourth day hopes of a result either way look unlikely.
Australian Holland completed his second half century for the county, in 121 balls, before he was bowled by Stuart Meaker.
Berg reached his fifty in 70 deliveries when a crashing six straight down the ground bringing up the milestone and eventually reached a classy 80 before he was caught behind off Jade Dernbach with the second new ball.
Berg had put on 93 with Abbott, and the South African created another frustrating tail-end stand with Fidel Edwards
The tenth wicket added 27, with Edwards scoring his highest Championship score of 20 before he was bowled by Tom Curran who ended with figures of 4 for 69.