The great diversity of quinoa allows variations in physiological, production, and compositional performance. This study aimed to evaluate six quinoa cultivars through the physiological and nutritional responses of their seeds. Different dynamics were identified in the plant height, and the number of leaves was adjusted to sigmoidal models with R2 greater than 0.97 and 0.77, respectively. The chlorophyll concentration varied through the phenological phases, as did the maximum quantum yield of photosystem II. Differences in the quinoa grains were found between CIEL*a*b* colorimetric coordinates and protein, carbohydrate, and fat contents. In this sense, quinoa cultivars manifest different biological behaviors associated with their genetic nature. Besides, a relationship between cultivars and seed composition was recognized. These results will allow researchers to study other significant differences between the precocity expressed by the Puno, Nariño, and Titicaca cultivars and those with a longer phenological cycle such as the Soracá cultivar.