Crossover exponent in O(N) phi^4 theory at O(1/N^2)

The critical exponent phi_c, derived from the anomalous dimension of the bilinear operator responsible for crossover behaviour in O(N) phi^4 theory, is calculated at O(1/N^2) in a large N expansion in arbitrary space-time dimension d = 4 - 2 epsilon. Its epsilon expansion agrees with the known O(epsilon^4) perturbative expansion and new information on the structure of the five loop exponent is provided. Estimates of phi_c and the related crossover exponents beta_c and gamma_c, using Pade-Borel resummation, are provided for a range of N in three dimensions.