Durham seamer Onions has admitted that he was disappointed to have been snubbed despite a three-season spell in which he has claimed 184 dismissals in 35 County Championship Division One appearances.
With England poised to make major changes for the opening Test of the summer, Onions is determined to maintain his domestic form and try to earn the international recall that he is desperate for.
"The bottom line is they wanted guys [in Australia] that are taller and, unfortunately, there is nothing I can do about that - I can't grow," Onions told reporters. "If England wanted me in Australia, they would have taken me and it was a massive disappointment for me that they didn't.
"My performances over the last four years have been of a high enough standard to get picked by England. But the captain and coach pick the team, I have to respect that and move on. It's taken a while to move on. The reason why I was so disappointed is because I want to play for England so badly.
"I'm still a strong believer that you train, put in performances and play as well as you possibly can to progress your game and play for England. I'll do that again this year and, fingers crossed, I'll be in for that first Test match against Sri Lanka [in May]. If not, then I'll keep on improving and be out there for Durham trying my hardest to win the championship again. I believe that I'm good enough to play for England. As long as my performances on the county circuit are good then I'm a believer they can't keep ignoring me."
Onions has taken 32 wickets at an average of 29.90 in nine Test matches, but has not played for England in any format since the five-day draw with West Indies at Edgbaston in June 2012.