As breeding has become increasingly specialized over the last decades, modern dairy breeds have mainly been focusing on milk production, producing bull and surplus female calves with low economic value. To address this dilemma, the present study evaluates how crossbreeding with the specialized beef breed Belgian Blue and pure breeding with Holstein-Friesian bulls affect calving ease and subsequent fattening performance, and carcass quality in Holstein-Friesian herds. For the study, pedigree information, calving information, as well as fattening performance and carcass quality parameters of 5,162 fattening bulls sired by either Holstein-Friesian (n = 4,607) or Belgian Blue (n = 555) sires from Holstein-Friesian cows in northern Germany were considered. Crossbred calves had higher birth weights and better carcass conformation ratings but also higher age at slaughter, carcass weight and average daily weight gain than purebred dairy calves, reflecting beef breeds’ superior muscle development. However, crossbreeding with Belgian Blue sires also increased the frequency of difficult births (dystocia), which has previously been shown to negatively impact calf health. The effect of parity was not relevant for fattening and carcass quality parameters but highlighted the present breeding practice of using beef sires in multiparous rather than in primiparous cows. Seasonal variations were also observed, with spring and summer-born bulls exhibiting faster weight gain.