How to move Lion installer to another Mac?

Question

I installed Lion on my MacBook Pro. Worked great.

Now I want to install it on my iMac, I don't want to re-download it from the App Store because it's a 3.5GB download and I have to pay for all my bandwidth (yes, I'm Canadian).

Is the installer executable on my MacBook Pro somewhere? If so, where is it and can I just copy it to the iMac and run it?

Thanks, Rob