This study aimed at evaluating the effects of underseeding alfalfa with different annual companion crops on forage yield, botanical composition, chemical composition, alfalfa establishment and alfalfa persistence. Treatments included alfalfa (13 kg/ha) seeded in solo (control) or with an annual companion forage such as sudangrass (15 or 20 kg/ha), ryegrass (20 kg/ha) or oat (90 kg/ha) which were assigned to a randomized complete block design. Experimental plots (4 replicates/treatment) were seeded twice (in May and June). All plots were harvested (3 and 2 times in May and June, respectively) at the budding stage of alfalfa. For each plot, harvested forage mix was weighed for total yield determination (DM basis). The harvested mix was then manually separated and weighed by forage type. Forage subsamples were chemically analyzed for NDF, ADF and CP. Alfalfa establishment and winter survival were determined by measuring alfalfa stem density in the fall of the seeding year and after one winter (spring) in the following year. Data were analyzed according to seeding dates using the GLM procedure of SAS. Overall, total forage yields were highest (P < 0.05) with sudangrass (3.6 T/ha) and lowest (P < 0.05) with control (2.4 T/ha) or ryegrass (2.1 T/ha). Alfalfa yield was markedly reduced (P < 0.05) with oat when compared with other companion crops. For June established plots, yield of companion crop was higher with sudangrass (average 1.6T/ha) and oat (1.2T/ha) than ryegrass (0.2 T/ha). However, sudangrass and oat produced forages with lower (P < 0.001) CP but higher (P < 0.001) NDF and ADF levels than control and ryegrass. Calculated relative feed values of forages were highest (P < 0.001) with control and ryegrass treatments. Sudangrass yielded more CP (1.4×) and NDF (1.9×) than control per hectare of cultivated land. Companion crops had no detrimental effects on alfalfa establishment and persistence. In conclusion, underseeding alfalfa with sudangrass may improve both forage and NDF yields for better feeding of dairy cows.