The protein content of wheat (Triticum aestivum L.) is a key factor in determining wheat quality and commercial value. To understand the underlying determinants of wheat protein abundance we are investigating protein turnover rate in wheat seed development using a new technique. By combining stable isotope labelling technology (15N)and proteome identifications, we can estimate the global protein turnover rate during wheat seed development and monitor the turnover rate of specific proteins of interest. We have used the Australian commercial bread wheat variety Wyalkatchem to showcase this method and what it can observe about the dynamics of protein accumulation during wheat seed development. Stable isotope labelling of hydroponically grown plants started when they reached 7 days post-anthesis, and immature grains were harvested after 3, 7 and 10 days. 15Nincorporation into newly synthesised proteins reached 2731% after 3, 7 and 10 days of labelling, showing that newly assimilated 15N from the roots is actively incorporated into seeds post-anthesis. In total, the turnover rate of 902 wheat proteins are detected by LC-MS/MS across three time points during grain development. Among these detected proteins, 253 proteins are involved in amino acid metabolism 82 in carbohydrate metabolism and 67 in photosynthesis-related machinery. This study provides new insights into the costs of protein synthesis for specific proteins that accumulate in wheat seeds and suggest new targets for maximising the dietary and financial value of this crop through altering protein composition.