The 16-year-old Wieber, who won the world all-around women's title in Tokyo last year, signalled she is close to her best by claiming her second consecutive U.S. all-around title earlier this month in St. Louis, Missouri.
Orozco, 19, also laid an early marker for Olympic selection, edging out defending champion Danell Leyva to claim the men's all-around crown in St. Louis as he chases his lifelong dream.
"Whether it's team, individual or all-around, I just want an Olympic medal in the sport I love so badly," the ever-smiling Orozco said while preparing for the first day of competition at the U.S. trials.
"I lay in my bed and I think about how it would feel to stand on that podium and get the medal put on my neck and be able to salute and be proud, knowing that all of these years and sacrifices have paid off.
"Being able to wear that medal in all its glory and honour, that would be amazing. That would be the moment that my life changes ... Being able to wear 'USA' on your chest is the most honourable thing that I can think of."
Orozco, a member of the U.S. men's team which won bronze at last year's world championships, edged past Leyva in the final event of the two-day competition to land the men's all-around title by 184.850 points to 184.800.
He sealed victory in the floor exercise, where he dismounted with a two-and-a-half twist.
"I can't even describe what I'm feeling right now," Orozco said. "Danell gave me such a great fight. The level of gymnastics was incredible."
While Leyva was disappointed to lose out in the battle for gold, the world parallel bars men's champion was delighted with his form heading into the U.S. trials.
"It was a really good competition for me," said the 20-year-old Cuban-American. "I think it was one of my best competitions ever, and I'm still not done peaking."
Wieber, who also won world championship gold in October in the team event, has been in scintillating form this year.
She won her third American Cup in the all-around ahead of compatriot Alexandra Raisman in March, then later that month led the U.S. to team gold at the Pacific Rim Championships in Everett, Washington, where she also landed the all-around title.
Just 16 days ago, Wieber successfully defended her U.S. all-around title at Saint Louis University, scoring 121.900 after two days of competition. Gabrielle Douglas was second (121.700) and Raisman third (120.950).
"It's so exciting to come out and win the championships in an Olympic year," Wieber said after securing victory with her signature vault, the Amanar.
Several other big names in U.S. gymnastics have converged on the Silicon Valley capital of San Jose this week in pursuit of places on the U.S. team at the London Games.
Olympic women's all-around champion Nastia Liukin is back at the age of 22 in a comeback bid, along with Beijing Olympic team captain Alicia Sacramone, who missed last year's world championships after tearing her Achilles tendon.
On the men's side, Jake Dalton, Jonathan Horton and Steven Legendre - each of them bronze medallists with the U.S. team at last year's world championships - are among 15 gymnasts competing for five spots on offer at the 2012 Olympic Games.