Light-emitting diodes (LEDs) are currently used as sole-source (SS) and supplemental (SL) lighting for microgreen production in indoor and greenhouse environments, respectively. The objectives of this study were to: 1) investigate the effect of SS LED light intensity (LI) on growth, yield, quality, and phytochemical and nitrate content; 2) quantify the effects of SL LED LI during the winter months on the growth and yield of microgreens. In the indoor environment, as SS LI increased fresh weight (FW), dry weight, total and reduced ascorbate and total anthocyanins increased in all genotypes, whereas total phenolic content was elevated in kale and arugula. Higher SS LI proportionally decreased hypocotyl length (HL) in all genotypes. In the greenhouse, leaf area and FW increased with increasing daily light integrals (DLI) in all genotypes. With the exception of sunflower, the dry weight, robust index, and relative chlorophyll content increased with increasing DLI, whereas specific leaf area decreased.