We evaluated the effects of differential levels of maternal nutrition induced by contrasting natural pasture allowances (days −23 to 122 of gestation) on newborn lamb’s muscle characteristics. Multiparous ewes were assigned to two nutritional treatments: High-pasture-allowance (HPA) ewes grazed on natural grasslands at 10–12 kg of dry matter (DM)/100 kg of BW/day; and Low-pasture-allowance (LPA) ewes grazed on 5–8 kg of DM/100 kg of BW/day. Samples (Semitendinosus and Longissimus lumborum) were collected from eighteen (9/treatment) male newborn lambs. LPA treatment reduced fiber diameter, nuclei number/fiber and muscle tissue proportion (P ≤ 0.0002) and tended to reduce fiber density (P = 0.097) in the studied muscles. A lower maternal pasture allowance reduced DNA concentration and increased protein/DNA ratio in both muscles (P ≤ 0.002). LPA treatment reduced (P = 0.046) protein concentration in the Semitendinosus. Muscles from LPA lambs showed greater mRNA expressions of MyHC-I and PAX7 (P ≤ 0.014), lower mRNA expression of IGF1 (P = 0.008) and tended to show increased mRNA expression of GLUT-4 (P = 0.09). The Longissimus from LPA lambs showed higher mRNA expressions of GLUT-4 (P = 0.032). Our results demonstrate that a reduced gestational pasture allowance induces several negative effects that might seriously limit postnatal muscle growth. Although LPA muscles showed some insights which could indicate an attempt to compensate for the negative effects (greater GLUT-4 and PAX7 expressions), the local endocrine (autocrine-paracrine) environment (reduced IGF1 expression) could be a major limiting factor for such compensation. Thus, a lower maternal pasture allowance affects newborn lambs muscle characteristics with possible future effects over animal health and meat-producing performance.