As well as a sneak preview of four all-new maps, it'll also feature exclusive unlockables that'll carry over to the full game when it releases on September 20.
The teaser is available only to Bulletstorm Epic Edition owners and those who pre-order Gears of War 3 at retail. That is, of course, unless you have a beta key. We have 15 codes to give away, and here's how to be in with a chance of winning one:
Step One: Follow our Twitter account @DS_Gaming
Step Two: Tweet the following: 'Follow @DS_Gaming and RT to win one of 15 Gears of War 3 beta keys http://tinyurl.com/dsgrs3 #gears3beta'
That's it! We'll pick give five random entrants each day on Tuesday, Wednesday and Thursday this week at 5pm BST. The contest is open to all Xbox Live users regardless of region, and please remember that our decision is final.