The 24-year-old has made just two appearances for the Lions this season and will make the switch to Brisbane Road until January 2.
O's boss Russell Slade has moved to bolster his midfield after losing QPR loanee Frankie Sutherland to a cruciate injury.
Slade told the club website: "Josh will bolster the squad and after the loss of Frankie Sutherland, it's an area that needs strengthening.
"He's got good experience at this level and in the Championship and is a very technical player with plenty of ability."
- Sports & Recreation
- Frankie Sutherland
- Russell Slade