MCA ignored quad because all their resources were being poured into their MCA DiscoVision Laser Videodisc format. They signed the co-development deal with N.V. Philips in September 1974 and and pulled all their best mastering/pressing engineers as well as the tech's responsible for maintaining the record presses, etc... and reassigned them to the MCA DiscoVision labs in Torrance (across the street from the Del Amo Fashion Mall!) MCA sent Philips a prototype player (since Philips hadn't gotten that far in development yet) and while Philips worked on engineering a consumer player that could be mass-produced and sold for a profit, MCA was responsible for the entire disc mastering and replication side of the format. (as it ended up, the final LaserDisc format was about 80% MCA/Universal Studio's invention with the remaining 20% being divided between Philips and Zenith)
For a short time, until they saw the handwriting on the wall that Quad was a non-starter on the market, they were engineering the LD format to use four FM audio carriers for quadraphonic reproduction and allow CinemaScope films with 4-track magnetic sound to be reproduced correctly in the home. Once they dropped that, to hedge their bets, they gave the FM audio carriers 80 kHz of bandwidth so additional channels could be added in a compatible manner if desired (Pioneer actually did utilize that industrally in the late 80's). In mid-1978, MCA and Pioneer, who had a joint company, Universal Pioneer, worked on a digital 4-channel laserdisc - it was a 14-bit format originally, then they changed to a 16-bit format. Because the Philips CD format seemed to be gaining momentum and Philips was courting Sony as a co-developer, MCA and Pioneer dropped all work on a 12-inch PCM disc.
So, MCA/Universal Studio's stayed out of the quad wars simply because they were working on the laser optical videodisc format. (As a side-note, I find it amazing that most people think either Philips invented the LaserDisc or that it was a Japanese invention, when in fact it was invented by Universal Studio's as a way to sell thier movies to the public at a low cost. Every optical-based disc we use today owes its existence to MCA/Universal Studio's - Discovision Associates
http://www.discovisionassociates.com, owned by Pioneer now, still exists as a patent licensing company and still collects royalties from Blu-ray discs and DVD's that employ, in some way, MCA DiscoVision technology. While the early patents have all expired, MCA kept a small team going to both buy relevant patents and work on extensions of existing patents to keep the optical disc covered by patent rights.)