Cultivating oleiferous brassica species, including rapeseed and mustard, is essential for increasing edible oil production in Bangladesh. However, the expansion of its cultivation faces challenges due to the dominance of rice-based cropping patterns. The present study evaluated 30 genotypes of B. campestris, B. napus, and B. juncea over two growing seasons (2022-2023 and 2023-2024) in Gazipur, Bangladesh, to identify short-duration high-yielding genotypes that are fit for cultivation in the 70-80-day gap between T-Aman and Boro rice cropping windows. An analysis of variance (ANOVA) revealed significant genetic effects (p < 0.001) for most traits, with no substantial differences between years. High genotypic coefficient of variance (GCV) and phenotypic coefficient of variance (PCV) values were observed for traits such as pods on secondary branches, secondary branches, mature pod plants^-1, and pods on primary branches, indicating consequential genetic control and selection potential. Correlation analyses demonstrated that grain yield was positively and significantly associated with biomass (BIO; r = 0.92***), thousand grain weight (TGwt; r = 0.87***), and phenological traits such as days to flowering and days to maturity, indicating their importance in selection. Among the four clusters, the highest yield-producing genotypes were grouped in Cluster III, while early flowering genotypes formed in Cluster II. Principal component analysis explained over 63% of the total variation, capturing heritability-controlled traits (grain yield, biological yield, mature pod plants^-1, pods on primary branches, and days to maturity) in PC1, whereas environmentally influenced traits (pod length, harvest index, and oil content) were in PC2. Heatmap analysis further confirmed distinct trait patterns, aiding in selecting specific genotypes with early flowering and high yield. Genotypes G12 (TH-2) and G6 (SAU Sarisha-1) produced moderate yields (average 1.79 and 1.75 t ha^-1, respectively) in the shortest possible time (average 78.81 and 76.79 days, respectively), making them suitable for cultivation in a gap between the popular T-Aman and Boro rice cropping window. These findings provide valuable insights to support sustainable agriculture and enhanced farmer profitability.