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High temperatures, coupled with arid environments, are a major constraint to quinoa (Chenopodium quinoa Willd.) production. Here, we tested the effectiveness of multiple phenotypic and physiological parameters useful in the selection of heat‐tolerant quinoa genotypes. Initially, we screened 112 quinoa genotypes for leaf greenness index under high‐temperature greenhouse conditions. Of these, eight genotypes were selected for field evaluations under irrigated and rainfed treatments in two locations over two growing seasons (2016–2017) in Washington State. Of these eight, four genotypes were selected as potentially heat tolerant (QQ74, Baer, BGQ 352, and Pison), and four were selected as heat‐susceptible (17 GR, La Molina, 3 UISE, and Japanese Strain). Spectral reflectance indices including normalized difference vegetation index (NDVI) and green NDVI, as well as multiple physiological parameters, such as stomatal conductance, leaf temperature, and area under soil plant analysis development (SPAD) value decline curve (AUSDC), were evaluated. Results show variability in stomatal conductance among genotypes with 17 GR and BGQ 352 having the highest stomatal conductance and QQ74 the lowest. Baer, Pison, and QQ74 had the highest NDVI value across environments, and Japanese Strain had the lowest. Best linear unbiased prediction values in AUSDC showed that QQ74 had the highest leaf greenness and Japanese Strain had the lowest; these were classified as heat tolerant and heat susceptible, respectively. The NDVI is a potentially useful measure to predict grain yield in quinoa. [ABSTRACT FROM AUTHOR]