QPR were booed off by their fans at full-time after another dismal home display - four days after their Carling Cup defeat to Leyton Orient.
Cardiff opened the scoring on 29 minutes. The home defence failed to clear former R's star Trevor Sinclair's corner and MacLean turned the ball home from close range.
The breakthrough came just seconds after Rangers goalkeeper Lee Camp had denied MacLean by sprinting from his line and blocking his shot after the striker was put through by Stephen McPhail's pass.
Up until then, both sides struggled to create clear-cut chances.
QPR striker Danny Nardiello and Parry both fired wide, before Rangers unsuccessfully appealed for a penalty when Nardiello's drive struck defender Kevin McNaughton's arm.
MacLean's goal came just as Cardiff were beginning to dominate and he would have put them further ahead had he not headed Parry's cross wide of the target when it seemed easier to score.
Less than a minute into the second half, Cardiff were very nearly punished for that miss.
Martin Rowlands picked out Stefan Moore, whose shot from the edge of the area beat keeper Ross Turnbull but bounced back off the post.
Cardiff were given another scare when Turnbull had to rush from his line to block Nardiello's effort after the striker managed to get in front of Roger Johnson.
Rangers were on top but just before the hour-mark McPhail crossed from the right and Parry headed in Cardiff's second goal.
John Gregory's men never looked like recovering and substitute Nick Ward missed a golden chance by shooting tamely at Turnbull from eight yards out.
Parry might have grabbed his second goal near the end but saw his header from MacLean's cross drift wide.