Having jumped a season's best of 1.89 metres earlier in the afternoon, beating Isobel Pooley in second place, Ennis then went on to run 12.92 in the hurdles, seeing off the threat of Tiffany Porter, who finished second with a time of 13.21.
Already part of the London Olympics team after qualifying in the heptathlon, the 26-year-old now competes in both the long jump and the 200 metres hurdles on Sunday. "It's great to come here and do well - it's a big weekend for British athletes," Ennis told the BBC.
"The crowd have been brilliant, it's a packed stadium and they have really got behind us. It was nice to know I had the qualification, so I could come here and sharpen up on the individual events."
There is unlikely to be a British representative in the women's high jump. The best of the rest was Emma Pooley but she needs a big improvement on her personal best to secure the standard - with the selection window closing in just over a week.
Dwain Chambers retained the men's 100 metre title with a time of 10.25, his fastest of the season, though still short of the 10.18 needed for Olympic qualification.
He has until July 1 to reach the A Standard time required to make the cut for the London Games. Adam Gemili, the 18-year-old who, crucially, has already clocked 10.18 this year, can now take his place in the Olympics team after finishing second.
Chambers was a happy, if relieved, man: "I was so scared because my heat in the semi-final didn't go well," he told the BBC. "I had pressure with all the youngsters like Adam coming through but I relied on my experience and it got me through.
"I still need to get the qualifying time and I have a chance to get it at the Europeans in Helsinki next week, so that is the next step.
"The pressure of trials is the hardest part and I am glad it's over. Now I can concentrate on getting the time."
For Gemili meanwhile, this is all still new. "I can't believe it, I don't know what to say," he said. "Now I have run the standard and finished in the top two, I will speak to my coach about what to do next."
World champion Dai Greene won the men's 400 metres hurdles final, coming in at 49.47 seconds, with Jack Green second on 49.88.
Greene is still some way off the stunning form that secured him the world, Commonwealth and European titles in the last two years but he did what was needed in Birmingham.
Nathan Woodward in third will need to rely on the selectors to complete the three available slots.
"It's good to get my spot on the team, it's just a shame the conditions weren't a bit nicer for hurdling," said Greene.
"To have [training partner] Jack alongside me was great as well and it's a great credit to our coach Malcolm Arnold and our training team."
Christine Ohuruogu, a gold medal winner at Beijing, won the women's 400 metres with a time of 51.89, followed by Shana Cox with 52.87.
"I am not delighted with the time but it was okay," Ohuruogu, who claimed a third UK title, said. "I have had a hard week, I have been training hard so I was ready to deal with the Olympic programme.
"I am going to rest for a couple of days now and then get ready for London 2012."
Lee McConnell and Nicola Sanders were third and fourth and will look to snatch the third available slot at the European Championships - and should be involved in consideration for the relay.
Ashleigh Nelson won the women's 100m ahead of Anyika Onuora, but neither have achieved the selection requirement. Abi Oyepitan, the only British sprinter with the Olympic A standard, withdrew from the final after suffering a niggle during the warm-up and world junior champion Jodie Williams pulled up with an apparent hamstring problem.
British record holder Greg Rutherford secured his Olympic place with a 8.12 metre best to win the men’s long jump, while JJ Legede and Chris Tomlinson finished second and third and will now head to the Europeans in a bid to state their claims.
Steph Twell's hopes of making a second Olympics appear over after she pulled out. Twell has one A standard time over 5,000m and needed to finish in the top two in Birmingham to guarantee her place on Team GB.
However, an untimely foot injury means she joins a growing list of absentees from the Alexander Stadium.
And she is also doubtful for the European Championships in Helsinki next week, where she'd need to run the A standard again to put herself up for consideration.
It completes a miserable few years for Twell, who has battled a succession of injury and illness problems - missing all of last season with a fractured ankle.
The women’s 5,000m final is on Sunday.
Luke Gunn heads to the European Championships needing another Olympic B standard to secure his place in the men’s 3,000m steeplechase at London 2012.
Gunn won his fourth national title with a battling sprint finish but remains confident he can achieve the required time in Helsinki next week.
"It's not ideal to leave it this late but I know I'm in the right shape," said Gunn.
"It will be a weird championship because nothing matters really but the time I run, placings are irrelevant.
"However, it's great to win a fourth national title - not many people have done it and there are some real legends of athletics in that club."
None of the first three in the women's 800m final - Lynsey Sharp, Jemma Simpson and Jessica Judd - have achieved the selection standard so positions in that event remain wide open ahead of the selection window closing at the end of this month.
Marilyn Okoro and Emma Jackson, who both could have booked their slots, with a top two finish came home a disappointing fifth and seventh.
Okoro in particular was inconsolable with her performance, as is her trademark she surged clear on her own but faded on the home straight, her tactics cruelly exposed by athletes she really should be beating.
Elsewhere, Sophie Hitchon retained her national women's hammer title with a best of 69.79m to become the first confirmed British track and field athlete to join Team GB and Steve Lewis also made sure of his selection with a fifth national pole vault title.
"It’s a bit unreal at the minute," said Hitchon. "I wanted to come out here and come first or second and that’s what happened. It’s all a bit surreal at the moment."
World 5,000 metres champion Mo Farah pulled out of the 1,500 final having won his heat on Friday, saying he needed to rest ahead of the European championships next week.
"Sorry I can't be at the trials today guys! I need to rest as much as possible and save my legs to defend my European title next week," Farah explained via his Twitter account.
Andrew Baddeley and Ross Murray posted a one-two finish in the 1,500.
“I feel relieved more than anything else,” said Baddeley. “It’s been a long road over the last 12 months and this is part two of part three. Part one was get the time; part two was the trials; part three is the Olympics. I haven’t been able to think about the Olympics until today. Now I can train harder.”
Andrew Osagie will look to underline his growing reputation after easing into Sunday's men’s 800m final.
Osagie was a confident heat winner while Michael Rimmer and Gareth Warburton, the two other athletes with the required A selection standard, also won with ease.
"It’s been an up and down year with lots of little niggles which is not ideal for a big year like this. Hopefully I’m coming to form at the right time," said Rimmer, a silver medallist at the 2010 European Championships and semi-finalist at the 2008 Beijing Olympics.
"I'm not going into the final with any negative thoughts. You’ve got to think like a boxer, you can’t think of anything negative.
"I’m going to go out there to try and win it. Hopefully I can do it, I’ve been there and done it before so I’ve got that experience."
Perri Shakes Drayton was the star of last year's trials, winning a 400m and 400m hurdles double but this year's British number one Eilidh Child was quickest into the women’s 400m hurdles final in 55.83 secs.
Shakes Drayton also won her heat while Megan Beesley, who still needs to run a personal best 55.50 A standard to stand a chance of Olympic selection, also progressed with ease but will need a big improvement in Sunday’s final.
In the absence of world silver medallist Hannah England, who is recovering from being spiked in Hengelo earlier this month, former world medallist Lisa Dobriskey progressed to the women’s 1500m final as the quickest qualifier. Rising star Laura Weightman, coached by Steve Cram, is expected to be her chief rival on Sunday after also winning her heat.
Lee Doran won the men's javelin with a personal best throw of 79.72 metres, still well down on the top level Olympic qualifying standard he needs.
Roald Bradstock, 50, who competed at the 1984 Los Angeles Games, became the oldest medallist in the event since 1936 with a world age group record of 72.78m earning him silver. British number one Mervyn Luckwell, who has the Olympic A standard, was absent from the trials.
Eden Francis will travel to the European Championships in Helsinki, after retaining her national women's shot title, still searching for another Olympic B standard throw.
Francis has a season's best of 17.24m - just four centimetres better than the lowest level selection distance - but won in Birmingham with a best of only 16.13m.
Phillips Idowu is likely to be the only British athlete in the men's triple jump after Larry Achike won the national title with a distance well off the qualifying standard.
Idowu is absent from Birmingham as he battles an unknown injury while British number two Nathan Douglas has been ruled out of the rest of the season.