Let G be a compact connected Lie group with Lie algebra g. Let M be a compact spin manifold with a G-action, and L be a G-equivariant line bundle on M . Consider an integer k, and let Q spin G (M, L k ) be the equivariant index of the Dirac operator on M twisted by L k . Let m G (λ, k) be the multiplicity in Q spin G (M, L k ) of the irreducible representation of G attached to the admissible coadjoint orbit Gλ. We prove that the distribution Θ k , ϕ = k dim(G/T )/2 λ m G (λ, k) β λ/k , ϕ has an asymptotic expansion when k tends to infinity of the form Θ k , ϕ ≡ k dim M/2 ∞ n=0 k −n θ n , ϕ . Here ϕ is a test function on g * and β ξ , ϕ is the integral of ϕ on the coadjoint orbit Gξ with respect to the canonical Liouville measure. We compute explicitly the distribution θ n in terms of the graded class of M and the equivariant curvature of L.If M is non compact, we use these asymptotic techniques to give another proof of the fact that the formal geometric quantification of a manifold with a spinc structure is functorial with respect to restriction to subgroups.