The ovarian reserve of primordial follicle oocytes is formed during in utero development and represents the entire supply of oocytes available to sustain female fertility. Maternal undernutrition during pregnancy and lactation diminishes offspring ovarian reserve in rats. In mice, maternal oocyte maturation is also susceptible to undernutrition, causing impaired offspring cardiovascular function. We aimed to determine whether programming of the ovarian reserve is impacted in offspring when maternal undernutrition extends from preconception oocyte development through to weaning. C57BL6/J mice were fed normal protein (20%) or low protein (8%) diet during preconception, pregnancy and lactation periods. Maternal ovaries were harvested at weaning and offspring ovaries collected at postnatal day (PN)21 and 24 weeks of age. Ovarian follicles were quantified (n=5/group). There was no impact of diet on maternal follicle numbers, however time to first litter was significantly delayed in protein restricted mice (n=11-12/group, p<0.05). In offspring, protein restriction significantly depleted primordial follicles by 37% at PN21 and 51% at 24 weeks (p<0.05). There were no effects of diet on other follicle classes. Histological analysis showed no differences in the proportion of proliferative follicles (pH3-positive), but increased atresia (cleaved caspase-3-positive, or TUNEL-positive), as well as altered patterns of mitochondrial (MTCO-1) and lysosomal (LAMP-1) distribution were detected in follicles of protein-restricted offspring at both ages (p<0.05). Our data show that maternal diet during the preconception period, in utero development and early life has significant impacts on follicle endowment and markers of follicle health later in life. In Australia, current National Health and Medical Research Council dietary guidelines are available for women during pregnancy. However, emerging evidence, including our findings, highlight the potential benefits for creating specific dietary guidelines and also improving clinical and public awareness of the importance of preconception diet for expectant mothers to develop healthy offspring.