The combination of Sr and O isotopes allow for the determination of crustal homogenization and hybridization during magma accumulation. We present oxygen isotope values of mineral separates, whole rock and in situ Sr isotope ratios of plagioclase from <1 Ma andesitic to dacitic composition lava flows from four volcanoes in the Central Andes with geographic relationship to the Altiplano Puna Magma Body (APMB): Uturuncu (1.1 Ma to 250 ka), Ollagüe (1.2 Ma to 130 ka), Aucanquilcha (1.04 Ma to 240 ka) and Lascar (49 ka to 0 ka). Sr isotope ratios were determined in situ using both laser ablation and standard cation exchange methods of plagioclase phenocryst and on whole rock powders. Oxygen isotope analyses were determined by laser fluorination of mineral separates. Mineral separate O isotope data has been re-calculated to account for mineral-melt 18O/16O-fractionation at various SiO2 contents to better constrain magma source variations and magma isotope heterogeneity with time and space. Variation in δ18OWR values for each lava suite is relatively limited (Lascar - δ18OWR =7.4-9.0‰; Aucanquilcha- δ18OWR =8.2-9.2‰; Ollagüe- δ18OWR =7.9-9.4‰) with the exception of Uturuncu which displays a large O isotopic value range (δ18OWR =8.7-11.4‰). Whole-rock 87Sr/86Sr ratios show a correlation of the lowest ratios along the arc front and generally increase towards the center of the APMB. Lascar (87Sr/86Sr= 0.7057-0.7067) and Aucanquilcha (87Sr/86Sr= 0.7058-0.7068) rocks exhibit the most homogeneous Sr isotope ratios and δ18OPL values, while Uturuncu exhibits the largest range of ratios (87Sr/86Sr= 0.7101-0.7165). Furthermore, in situ 87Sr/86Sr ratios of Uturuncu plagioclase phenocrysts exhibit more variation within a single crystal (87Sr/86Sr= 0.7098-0.7165) than the observed at all four volcanoes. Uturuncu magmas contain the highest variability, both in plagioclase mineral separates and whole rock values, and therefore must contain high 18O crustal material. This hypothesis is further supported by the textures and isotopic variation within plagioclase phenocrysts suggesting repeated crustal contamination followed by mixing occurring in the shallow crustal reservoir. Conversely, the arc front source is more homogeneous and hybridized, and arc-front magmas assimilate similar composition crustal material.