A macroscopic model of opposed flame spread based on the SIMPLE algorithm was examined. Features of flames spreading over thick degrading combustible materials were described utilizing the moving boundary method. Numerical predictions of flame spread speed showed good agreement with the experimental data. Comparisons were made, for flame spread over thermally thick samples of PMMA for several flow velocities, with numerical predictions for the primitive quantities temperature, velocity field, and surface regression. Quantities derived from primitive variables included the mass flux, the surface heat flux and the heat loss from the solid. The velocity gradient in the airflow boundary layer and the temperature gradient in the solid interior were examined. Other quantities also examined were the wall heat flux and the burning rate of the regressing pyrolyzing surface along with their relation to the rate of supply of oxidizer (air).