Two indigenous rangeland forage species viz. Cenchrus ciliaris L. (UAE) and Coelachyrum piercei L. (UAE) collected under ICARDA- APRP Phase- I were investigated along with Chloris gayana L., a popular perennial grass, under ICARDA- APRP Phase-II to understand the influence of early and late forming tillers on their seed weight (with husk) per se and seed quality from August 2003 to August 2004 at two locations of Oman namely Livestock Research Center, Rumais (LRC) in South Batinah governorate and Jimah Agriculture Research Station (JRS) in the Interior governorate. Samples of inflorescences of both early and late forming tillers of three grass species were collected about one week after physiological maturity of inflorescences. The results of the investigations spanning five harvests indicated the existence of differential expression of the seed related traits in three grass species studied in two types of tillers viz., early forming and late forming, in different times of harvests in both the locations. The above results indicated that early forming tillers possessed all seed related traits like inflorescence weight (mg), seed weight (with husk)/ inflorescence (mg), seed recovery (%) from inflorescence and germination per cent significantly superior to late forming tillers in respect of grass species studied. Hence, it is recommended that while harvesting the seeds in forage grass species emphasis should be given to harvest more proportion of seeds from early formed tillers than from late formed tillers to get optimum quantity of better quality seed. The results have significance particularly in producing pre-basic, basic, breeder and foundation seed of grass species.