Do big tech companies require on site interviews? I'm a postdoc in the US, from Europe originally. I plan on applying for research scientist positions at big tech companies in Canada e.g. Google, uber, etc (I want a change from the US). 

My problem is that my travel outside of the US is restricted on my current visa. Is it possible to get positions at these companies without doing an onsite interview? Alternatively can I interview for positions at their offices within the US for positions in Canada? Has anyone had a similar issue or have any knowledge that may be helpful.

Thanks!
Every company will have its own procedures and likely other procedures that represent exceptions to the normal procedures. If a company is interested in you they will probably be able to find a way to make an interview happen. There are a lot of possibilities. Online interviews, via Skype and such, are becoming common at the early stages, at least, if not for final acceptance. Meeting a member of staff at a professional meeting in the US is a possibility. 

If they show interest and want an interview discuss your travel restrictions. The problems with US visas and such are well known, especially, I think, in Canada. If they are interested enough then they will probably suggest something. 

But at some point in the hiring process, companies like to have you visit your potential work site to meet a lot of people you'd be working with so you can get a sense about one another. They also like to show off the great work environment, especially if they really want you to join. That might be harder to arrange.