I know from the web interface, you can send messages to up to 10 people. However, I haven't figured out how to send an SMS message to multiple people using the Google Voice Android app. Is it possible? If it is, how?
Like the people who responded said, yes you can, but you will not receive group responses - you get each response as if it was a 1-1 SMS from whoever responds to your original group SMS.
Somewhat defeats the purpose of being able to do this when it can't handle things the other way around.
Also incoming group messages are split the same way, as if it was a 1-1..
It's not possible with the stock Google Voice App. You will have to download an alternative Google Voice SMS app like the aptly named "Google Voice SMS" to send a message to multiple people. That app costs $2 but there are free apps available.