During the Reaper invasion, Coats spent three days inside the Big Ben clock tower, shooting at anything that moved.
During the final battle on Earth, Coats provides covering fire as Commander Shepard is extracted by a UT-47 Kodiak Drop Shuttle. Later on he is ordered to coordinate the artillery strikes by Admiral Anderson as Shepard's team makes their way to the Citadel. He can also be heard on the radio, after Shepard is hit by Harbinger, ordering all surviving soldiers to fall back from the attack on the beam.
If Shepard chooses to activate the Crucible, then Coats, Gabriella Daniels, and Kenneth Donnelly (provided the duo also survived the war) will be seen helping in the reconstruction of London. If Shepard didn't bring most of the Galaxy's might into the final battle Major Coats will instead be seen smoking a cigarette amid the ruins of London.
- Coats first appeared inside of Big Ben during the debut trailer for Mass Effect 3 and appeared again in the full "Take Earth Back" trailer. Prior to the initiation of Hammer's final attack, he mentions in passing that he had spent some time holed up in Big Ben.
- Nick Boulton, the voice actor for Coats, also voices the male Hawke in Bioware's Dragon Age series.