ABSTRACT Methionine -an essential amino acid that has to be provided by nutrition- and its metabolite S-Adenosyl methionine (SAM) are indispensable for cell proliferation, stem cell maintenance and epigenetic regulation 1–5 , three processes that are central to embryonic development 6 . Previous studies using chronic dietary restriction of methyl donors prior to and during gestation indicated that methionine restriction (MR) is detrimental to the development or growth of the neocortex 7,8 , however, the consequences of acute MR have not been extensively studied. Here, we designed a dietary MR regime coinciding with the neurogenic phases of neocortex development in the mouse. Our results indicate that dietary MR for 5 days leads to a severe reduction in neocortex growth and neuronal production. In comparison, growth of the liver and heart was unaffected, highlighting an organ-specific response to MR which was also observed at the cellular and molecular levels. Progenitor cohort labeling revealed a time-dependent sensitivity to MR and cell cycle analyses indicated that after 5 days of MR, progenitors are stalled in the S/G2 phases. Unexpectedly, neocortex growth reduction induced after 5 days of MR is completely rescued at birth when switching the dam back to control diet for the remaining of gestation, uncovering a mechanism of catch-up growth. Using multiplexed imaging we probed metabolic and epigenetic markers following MR and during catch-up growth and show that pyruvate metabolism is rewired in progenitors. Altogether, our data uncover a transient state of quiescence in G2/S which is metabolically distinct from G0 quiescence and associated with efficient catch-up growth. More globally, our study highlights both the extreme sensitivity of the developing neocortex to acute dietary changes and its remarkable plasticity.