In this work the performance of annealed proton-exchanged (APE) waveguides in periodically poled stoichiometric lithium tantalate (PPSLT) for high power applications in the C-band is investigated. Two APE-PPSLT chips comprising 50 waveguides produced with different poling periods and mask width for proton-exchange (PE) were characterized. The performance of the PPSLT devices was also compared with a periodically poled lithium niobate (PPLN) waveguide. Despite lower efficiency, no photorefractive issues or deleterious green light emission were observed in the PPSLT waveguides. The experimental results suggest that the homogeneity of the PPSLT waveguides can be further improved, which will enhance their efficiency.