Abstract: Chicory is an important forage plant for animal husbandry in south China. The yield of chicory is closely related to the length of the plants’ vegetative growth phase. In this study, Arabidopsis AtmiR156a was over-expressed in chicory and a total of 140 independent lines of transgenic plants were obtained. PCR analysis detected 94.3% positive expression in these plants. q-PCR analysis showed that, compared with the wild-type chicory used as control, the expression of AtmiR156a was promoted by 7.9 times in the transgenic plants. Germination rates for the AtmiR156a over-expressed lines were similar to that of the control, but the leaf emergence rate was significantly faster. Bolting time and flowering time were delayed by 20.2 and 27.3 days respectively in the AtmiR156a over-expressed lines. However, plant height was reduced, which led to similar annual forage yields for both the wild type and transgenic plants. Forage quality was analyzed via a first cutting of leaves. The results showed that crude protein content was 3.7% higher and fiber content was 2% lower in the AtmiR156a over-expressed lines; other quality traits showed no significant differences from the control seedlings. Our results establish an efficient method for the genetic transformation of chicory. The experiment also created a pool of late-flowering and fast-growing germplasm resources, laying a foundation for the breeding of high-yield and cutting-resistant chicory varieties. The results provide a reference for theoretical studies and practical applications aiming to improve chicory performance through the use of genes from other crops.