High tunnels are used to modify the crop environment by trapping solar energy, providing protection from unfavorable weather events, and extending the growing season in temperate regions. This project assessed yield and quality in three independent cultivar trials of warm-season crops tomato (Solanum lycopersicum L.), bell pepper (Capsicum annuum L.) and cucumber (Cucumis sativus L.) grown under high tunnel production compared with an outdoor field in eastern and western North Dakota. Tomato yields in the high tunnel were increased by 1.4 times over the field trial yields. Yields from the pepper cultivar trials both inside the high tunnel and outside field were comparable to one another at 1.24 kg plant-1 and 1.06 kg plant-1, respectively. Cucumber yields in the high tunnel were increased by 1.7 times over the field trial yields. Results indicate that in North Dakota, high tunnels extended the growing season, and increased production relative to field conditions.