Substitute Paul Peschisolido salvaged a draw for Derby with a dramatic late leveller to cap an entertaing match.
Bale celebrates scoring for Southampton
County dominated the opening 45 and deserved their lead from Seth Johnson's strike after Steve Howard's knockdown.
But after the break Southampton stepped it up and Gareth Bale drew them level with a wonderful, curling free-kick.
Former Ram Grzegorz Rasiak played in substitute Bradley Wright-Phillips who rifled in a fierce shot for Saints before Peschisolido's 90th-minute goal.
The hosts looked to have run out of ideas and puff before Peschisolido arrowed a low shot into the corner of the net.
Inigo Idiakez had seen a shot beaten away by Kelvin Davies and Howard was unable to get enough power in his header from a Giles Barnes cross.
Barnes, the day after his 18th birthday, showed some delightful touches, particularly in the first half as Derby ran the show in their first competitive match under Billy Davies.
But Barnes was soon overshadowed by another of the Championship's brightest young prospects - 17-year-old Bale.
His left-footed free-kick, following Ryan Smith's foul on Alexander Ostlund, beat Lee Camp's despairing dive and looked like setting Saints on the road to victory.
And after Wright-Phillips had put Southampton in front on his debut they had chances for a third, most notably when the former Manchester City striker broke on the right only to see his pass to Rasiak cut out by Darren Moore's sliding, defensive lunge.
And Peschisolido's goal, from Morten Bisgaard's pass, added insult to injury for George Burley's team who also saw Claus Lundekvam and Ricardo Fuller go off injured.
Lundekvam, sent off on the first day of last season, lasted six minutes into this one before going off with a badly swollen ankle and a blow to the head.
Striker Fuller pulled his hamstring six minutes into the second half.
Derby manager Billy Davies said:
"I thought for 60 minutes we did what we wanted to do, but after that too many players ran too deep and stopped pressing.
"For an away team we allowed them too much time on the ball.
"That said, Southampton have already been crowned champions by some so we have to be pleased in one sense."
Southampton boss George Burley:
"Having Claus carried off after five minutes was a real blow. But I thought after the break we played some quality football.
"It was certainly a better performance by us than in the first 45.
"We have a lot of new faces and it takes time to build a team. But in the second half we got forward quicker."
Derby: Camp, Edworthy, Michael Johnson, Jackson, Moore, Ryan Smith (Bisgaard 62), Seth Johnson (Peschisolido 84), Idiakez (Bolder 78), Barnes, Tommy Smith, Howard.
Subs Not Used: Oakley, Nyatanga.
Goals: Seth Johnson 35, Peschisolido 90.
Southampton: Davis, Pele, Lundekvam (Ostlund 6), Baird, Bale, Skacel (Surman 90), Wright, Belmadi, Viafara, Rasiak, Fuller (Wright-Phillips 54).
Subs Not Used: Poke, Dyer.
Booked: Wright-Phillips, Skacel.
Goals: Bale 62, Wright-Phillips 68.
Ref: A D'Urso (Essex).