By introducing triangular holes into oxide confined 850nm monolithic vertical-cavity surface-emitting lasers (VCSELs), single-transverse-mode operation has been obtained for large oxide apertures of 14-15 microns. The two-dimensional triangular holes etched on the device surface were aligned circumferentially along the aperture perimeter, with their tips surrounding the device center. When the holes had a relatively large lateral penetration into the oxide aperture, the holey VCSEL lased with a single spot near field pattern with a high side-mode suppression ratio (SMSR) of 45-50dB, and an output power of 2mW. In this case, it is assumed that the triangular holes are acting as a highly mode selective loss mechanism. On the other hand, when the penetration of the holes was relatively small, an SMSR of 40dB was obtained from a large area "floral" near field pattern, with a record high single-mode output power of 7mW. The lasing spectrum and far field intensity profile of this "floral" type emission indicates that it is a somewhat deformed fundamental mode that is extending over the whole device, and oscillating in-phase. The ability of triangular holes to suppress high order modes in large area oxide confined VCSELs should be effective for systems with wavelengths other than 850nm as well.