Monte Carlo simulations are used to calculate monomer distribution profiles and adsorption isotherms of moderately dense end-grafted and adsorbed polymer chains. Modified variants of the pivot algorithm on a cubic lattice are combined with a fixed end points pivot algorithm to allow simulation in regimes where normal pivoting is ineffective due to excluded volume effects. Scaling behavior that agrees with analytical theory for low density and a brush is obtained for the end-grafted case, which illustrates the accuracy of this method applied to polymers that are overlapping. For polymers in the solution phase a Monte Carlo move of the center of mass of the polymer is added to the normal pivot moves. The surface excess is obtained by integrating phi(z)(-)phi(b) and can be treated by the Langmuir model to obtain the apparent maximum surface excess (Gamma(exc)(max)) as a function of the bulk monomer concentration (phi(b)). It is found that the presence of end-grafted nonadsorbing polymers can affect competitive adsorption of different length chains. In particular, high molecular weight polymers may be preferentially excluded from a polymer-grafted surface, unlike a bare surface.