This paper presents a time dependent boundary layer flow and heat transfer of an incompressible Oldroyd-B nanofluid past an impulsively stretching sheet. Heat transfer analysis is carried out by taking thermal conductivity as a function of temperature. The non-dimensionalized partial differential equations are solved using bivariate spectral quasi-linearization method). The employs the concept of quasi-linearization to obtain a linear system of partial differential equations which is subsequently solved using a spectral collocation method that uses bivariate Lagrange interpolating polynomials as basic functions. This method is found to converge rapidly and is very effective in yielding accurate results. Numerical results have been presented graphically to illustrate the details of flow and heat transfer characteristics and their dependence on some of the physical parameters.