  We present a method which, starting directly from QCD, permits a systematic
gauge-invariant expansion to be made for all hard processes involving quarkonia
in powers of the quark relative velocity, a small natural parameter for heavy
quark systems. Our treatment automatically introduces soft gluons in the
expansion. Corrections arising from the incorporation of gauge symmetry turn
out to be important for decay and fragmentation processes involving $Q \bar{Q}$
systems. The contribution of soft gluons is shown to be of higher order in $v$
and so is neglected for calculations done upto and including O($v^2$).
