The main objective of this study was to assess the combining ability and heterosis for rice grain yield and quality traits to recognize the most desirable genotypes for rice breeding programs. Six lines were crossed to three testers in this study and the resultant eighteen hybrids. Parents and their 18 F₁ crosses were evaluated under two separate irrigation experiments; the first and second experiments were irrigated every four days (normal condition) and the second experiment was irrigated every twelve days (a stress condition), respectively. Results indicated that water deficit treatment was significantly reduced all the studied traits except for amylose content (%).Two crosses, Sakha107 x M 206 and Sakha107 X Sakha Super 300 had the highest desirable mean values for hulling (%), milling (%), head rice, grain thickness (mm), and grain shape. Three crosses namely, Sakha107 x M206, Sakha107 X Sakha Super 300 and Sakha108 x Sakha Super 300 had the highest mean values of no. of panicles/ plant, panicle length (cm), panicle weight (g), 1000- grain weight (g), grain yield / plant (g) and fertility (%). The varieties, Sakha 107 and Sakha108 as line, M206 and Sakha super 300 as a tester were the best general combiners and could be used in rice breeding programs for improving all the studied traits under both conditions. The most desirable mid-parent and better-parent heterosis for grain yield and quality traits were detected for the crosses, Sakha107 X M206, Sakha108 X M206 and Sakha107 X Sakha Super 300 under both and across environments, respectively.