In two sessions, the GB&I team won six of a possible eight points to extend its lead to 11 1/2 - 6 1/2.
In the morning greensomes, GB&I won three of the four matches and the other match was halved.
The afternoon also went GB&I's way as it halved the opening match, and won the final two.
"Obviously, we are absolutely delighted. It's been a great day, things went really well for us," stated GB&I captain Paul McGinley. "Our concentration levels were really good, and we were really up for it. We're really motivated and really concentrated and we are really focused. We got the job done."
Italians Matteo Manassero and Francesco Molinari parred the 18th to halve their match with GB&I's Robert Rock and Jamie Donaldson.
World No. 2 Lee Westwood and David Horsey won three straight holes from the 10th en route to an easy 4 & 3 win over the Continental Europe duo of Raphael Jacquelin and Nicolas Colsaerts.
This is the first Seve Trophy since the death of the tournament's namesake, the great Seve Ballesteros.
Bjorn and Hansen won the fourth and fifth with pars to go 1-up, but Fisher and Foster evened things with a birdie on No. 6. Hansen rolled in birdie efforts on the seventh and ninth, and his side took the 10th with a par to 3-up.
The duos traded wins on 11 and 12. Foster and Fisher got to 2-down with a birdie on No. 14, but the Continental Europe team birdied the 16th to close out the match.
Molinari and Manassero were 1-up after six holes as they claimed three of the first six, while Rock and Donaldson took the first and fifth with birdies.
Rock and Donaldson ran off three wins in a four-hole span from the eighth to go 2-up. The Italians squared the match with consecutive birdies on 13 and 14. Rock and Donaldson reclaimed the lead with a birdie on 16, but they three- putted for bogey at the last to halve the match.
The final two matches easily went to GB&I.
Jacquelin and Colsaerts won the third and fourth to go 1-up. Westwood and Horsey roared to five wins in a seven-hole span from the sixth to move 4-up.
Jacquelin and Colsaerts ended that run with a win on 13, but Horsey chipped in for birdie on the 14th to reclaim their 4-up lead. The match was over when the teams halved the 15th with birdies.
"The last thing we will be is complacent, because I've played in teams where you've had a big lead and it evaporates quickly if you start getting down in the early games," Westwood stated. "We'll come out with the same intensity as today I'm sure and try to get on the board early."
Larrazabal and Noren were conceded the second and fourth, then the teams traded wins on the sixth and seventh. It was all GB&I from there. Dyson and Poulter won four of five holes from the ninth to 13th to grab a 2-up lead. After three straight halves, Dyson chipped in for eagle on the par-five 17th to end the match.
NOTES: On Sunday, all 10 players tee it up in singles action...After the big day for GB&I on Saturday, McGinley's team needs just 2 1/2 points in the singles matches to retain the trophy...Three points in the singles will give GB&I its sixth straight win at this event, with the Continental Europe team winning just the inaugural tournament back in 2000.