How can I make scaleable embedded video files in blog posts?

When I embed a video into my blog posts in Easyblog it says I can change the dimensions but then when I change them it stays the same small size. It's just reverting back to some default option. So then I just took the iframe code from Vimeo and inserted it directly in. This worked as the content displayed at the right size. However, when the screen size is scaled down the iframe doesn't contract and then overlaps onto other modules.

Just wondering what the best solution around this would be?

Cheers

B