Boss Paul Sturrock told the club website: "With the postponements and busy Christmas period coming up we felt it would be wise to hang on to Antonio.
"He's shown glimpses of what he is capable of during matches."
Sturrock added: "But I believe there is more to come which he will hopefully show over the next four weeks."
There is a recall clause in German's deal, meaning Rangers boss Neil Warnock can summon him back to Loftus Road with 24 hours notice.
Source: BBC Sport
Source: BBC Sport