Voice chat is possible in Halo Master Chief Collection, even if it is slightly limited right now. You can choose to disable it all together, or set it up so that only your team mates can hear you.
By default, the game uses a push to talk system, and not an open-microphone setup. If you’re just wanting the default key to use push to talk, it’s ‘V’. However below you can find the menu to configure just who you want to be able to hear you.
This guide is suitable for the Halo Master Chief Collection, which includes Halo Reach, Halo Combat Evolved, Halo 2, Halo 3, Halo 3: ODST and Halo 4. For more Halo MCC Guides, make sure to check out our dedicated area here!
Using Voice Chat in Halo MCC
To start, you can change the Voice Chat Configuration inside the Audio section of the Settings Area. Specifically the bottom option, which allows you to switch between Off, Squad, Team and all.

Choose the option must suited to you, with the option being Off if you obviously don’t want to talk to, or listen to anyone in-game. There is also a voice chat slider available for you to change how loud other players are in this menu.

At the moment, the default talking method is ‘Push to Talk’. This means you have to press a key to talk to other players (there’s no option to change this). On PC, this has been defaulted to ‘V’, and can’t be changed right now. Whilst to use text chat, you can press ‘J’.
Currently, there doesn’t seem to be a button for controllers. It’s expected that changes and more customisation will come to the voice chat feature in future updates, including the ability to change the default keys.