This study was undertaken to evaluate the response of teosinte (Zea mexicana L.) and intersubspecific hybrids to heat stress, in particular productivity. Unlike maize (Zea mays L.), teosinte demonstrated thermophilic properties, namely lower heat injury, sustained chlorophyll content under heat stress (36−45°C) and high percentage survival of seedlings (at 55°C). Teosinte also had the ability to produce large plant biomass (27% and 55% higher yield than maize under non-stressed and stress conditions, respectively) and therefore could be exploited as a forage crop. However, teosinte forage had low animal intake (1.48 kg day^–1) because of high pubescence density (10.38 view^–1) and low sweetness (9.90°Brix). There was a high percentage of heterosis in variable intersubspecific crosses and traits, and a high magnitude of over-dominance for many traits, for example 5.93–7.06 for total biomass plant^–1. Hybrids showed additional advantages, including high oil (20% and 4%) and protein (14% and 25%) contents compared with teosinte under non-stressed and stress conditions, respectively. Moreover, inter-subspecific hybrids were also resistant to heat stress, with the capacity for sustaining growth for a longer period (20% and 33% higher than maize under non-stressed and stress conditions, respectively). Genetic distance between parents—calculated from stable agronomic traits—could be used to select parents for high heterosis under both heat stress and non-stressed conditions.