The beam quality of 800 nm AlGaAs/GaAsP broad-area (BA) laser diodes with large optical cavity (LOC) waveguide structures was studied under high power conditions. The LOC structures consist of a tensile-strained GaAsP single quantum well embedded in AlGaAs layers forming 1 and 2μm thick waveguide cores. A low beam divergence of 51 o respectively 46 o (full width at 1/e 2 maximum) is obtained in fast axis direction. BA diode lasers with 2 mm cavity length and stripe widths of 60, 100 and 200 μm show beam quality factors M 2 along the slow axis of about 12, 16 and 35 at 2 W output power, respectively. M 2 also weakly depends upon the waveguide width and is slightly smaller for the 2 μm waveguide core if the stripe width is less than 100μm.