The combustion of two-dimensional laminate propellants of ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB) is investigated experimentally and theoretically. The experiments use UV emission and transmission imaging to obtain simultaneous information about flame structure and burning surface profile for pressures ranging from 2 to 55 atm. The modeling uses numerical computations based on finite-rate chemistry with simplified kinetics and a free surface. Results show that flame-surface structure is a function of length scale (in this case, fuel-layer thickness), pressure, and equivalence-ratio disparity between the non-premixed fuel and oxidizer regions (binder-matrix equivalence ratio). Factors that promote split (diffusion) flamesurface structure are large length-scale, high pressure, and large equivalence-ratio disparity. The opposite factors (including oxygenating the binder) promote merged (premixed) flame-surface structure. For oxygenated binder loaded to the monomodal-AP limit (fine-AP/binder = 76:24) the transition thickness between split and merged structure is 5 to 10 times larger than that for pure binder. A correlation is shown between this transition and the optimal thickness that maximizes regression rate (at a given pressure). It has been determined both computationally and experimentally through the use of triple-layer laminates that the flame-surface structure at the center of the laminate is relatively uninfluenced by the outer boundary conditions. This provides firm justification for using the simpler, single fuel layer laminates to validate computational simulations through characterizing the effects of pressure, thickness, and binder equivalence ratio on flame and burning surface structure.