Highbush blueberry (Vaccinium corymbosum) fruit of the cultivars `Bergitta', `Bluegold', and `Nelson' were harvested at six stages of maturity and evaluated for their antioxidant capacity and anthocyanin and phenolic content. Fruit of the four earliest maturities were also stored at 20 °C for up to 8 days. At the time of harvest, fruit of different maturities had substantial differences in their anthocyanin content, and less marked differences in phenolic content and antioxidant capacity. Substantial anthocyanin synthesis occurred in under-ripe fruit during 20 °C storage, and varied depending on fruit maturity at harvest. Total phenolic content changed very little during storage, and there was no change in fruit antioxidant capacity. The results suggest that anthocyanin phenolics are formed on or off the plant, primarily from other pre-existing phenolic components. Whether phenolics are present as anthocyanins or other colorless forms, has relatively little impact on antioxidant capacity.