The 27-year-old agreed a two-year contract with the O's on Friday and will join up with his new club once his contract with Derby County expires later this month.
Legzdins didn't make a single appearance for the Rams last season and now wants to establish himself as a regular with Orient.
"I can see how that togetherness can help you achieve great things and so I wanted a club with a close set of lads with great camaraderie," he told the Derby Telegraph.
"Last year was disappointing for me for various reasons and I played fewer games than I'd hoped, but the year before I played 33 games in the Championship.
"That's my ambition, to play games. I don't want to be number two goalkeeper."
Orient came so close to promotion from League One, losing to Rotherham United in a penalty shootout last month.