Near-stoichiometric lithium tantalate (SLT) crystals were produced from congruent lithium tantalate by vapor transport equilibration (VTE), and several important optical and ferroelectric properties were measured. The effect of vapor transport conditions and surface preparation on reproducible ferroelectric engineering of SLT have been studied. Control of these effects along with dramatic decreases in the sensitivity to photorefractive damage and 532-nm absorption has allowed near-room-temperature generation of 10 W of CW 532-nm radiation by second harmonic generation from 29 W of 1064-nm radiation in a 4-cm-long device. Devices periodically poled for watt-level generation of 589-nm radiation by both second harmonic and sum frequency generation have also been demonstrated. Control of ferroelectric properties allowed periodic poling down to a period of 5 um suitable for generation of 458.3-nm radiation by second harmonic generation. Investigations into the application of periodic poling and vapor transport equilibration on rotated-cut crystals have led to the development of aperture-scalable, quasi-phasematched devices suitable for high peak- and average-power nonlinear optics.