Halo Master Chief Collection (Halo 3: ODST)

Halo ODST for the Xbox One is an Add-On for the Master Chief Collection. you must own that in order to play it.

When you fire up the Master Chief Collection, you should be able to start a campaign (under Halo 3) for ODST.

Halo 3:ODST is listed under the Halo 3 section in the Master Chief Collection, have you checked there?

Hey there,

The Halo Master Chief Collection does not include Halo 3: ODST, but it should include Halo 4: Spartan Ops. Halo 3: ODST is available on the Xbox Store as an add-on for Halo: MCC.

Hope this helps!

The Original Xbox version of Halo CE is only backwards compatible on the the 360
To play it on the One X you would need Halo The Master Chief Collection which includes
Halo CE Anniversary

Halo 2 Anniversary

Halo 3

Halo 3 ODST - available as add on content

Halo Reach - available as add on content

Halo 4

And at the moment it is HALF PRICE in the Microsoft store (with ODST and Reach included too)

Buy Halo: The Master Chief Collection - Microsoft Store en-GB

How does one go about finding the ODST download?

"The re-mastered version of the campaign for “Halo 3: ODST” in “Halo: The Master Chief Collection” and the re-imagined “Halo 2: Anniversary” version of the “Relic” multiplayer map will be available in spring 2015. Both projects were not part of our original
development plans, but as a result of community feedback, and to do something special for our fans, both are now in development. The campaign for “Halo 3: ODST” will be delivered via a free download token for eligible players1 of “Halo: The Master Chief Collection,”
and “Relic” will be included as part of a free content update for the game."

https://www.halowaypoint.com/en-us/...alo-the-master-chief-collection-thank-you-faq