Holloway, who began his second spell in charge of the Championship club on Friday, previously worked with Bircham during his time as Millwall boss.
Bircham has since coached in the USA at Chicago Fire and Arizona United.
The 38-year-old was on the coaching staff at QPR, first as youth team coach and then development squad coach, between 2009 and 2014.
Having also made 167 appearances during five years as a player at Loftus Road, he described his return to the R's as "a dream come true".
Former Canada international Bircham told the club website: "QPR are the only club I'd have moved back to England for.
"The opportunity to work with [Ian] again, at a club that we both know inside out, was just too good to turn down."
David Oldfield and Dirk Heesen, part of the backroom staff under Holloway's predecessor Jimmy Floyd Hasselbaink, left the west London club on Monday.
New Queens Park Rangers manager Ian Holloway has appointed Marc Bircham as first-team coach.