Hairy vetch (Vicia villosa Roth) fixes N for corn (Zea mays L.) production, and cereal rye (Secale cereale L.) accumulates soil N to reduce potential N losses. The objective of this research was to identify optimum seeding rates of vetch-rye cover crop mixtures at Coastal Plain and Piedmont locations in Maryland. Mixtures evaluated were 14, 21, and 28 kg vetch ha−1, and 47 or 94 kg rye ha−1 in complete factorial combination. Pure vetch, rye, and no cover crop were used as controls. Cover crops were killed in early April (early kill) and early May (late kill), followed by no-till corn without fertilizer N. Corn grain yields were significantly higher following late-killed covers. Coastal Plain grain yields ranged from 3.1 to 7.0 Mg ha−1 and Piedmont yields ranged from 5.2 to 10.7 Mg ha−1. Within each kill date, corn yield was highest following vetch, lowest following rye, and intermediate following all six mixtures. Cover crop yield increased by 160% in the Piedmont and 83% at the Coastal Plain location when kill was delayed. Except for pure rye, N content was 1.6 to 2 times greater by the late kill date. Total N content was equal for all vetch-rye mixtures at each date and within location, ranging from 74 to 109 kg ha−1 for early kill, and from 136 to 219 kg ha−1 for late kill. Carbon-to-nitrogen ratios (C/N) were 25:1 for all mixture combinations at the Piedmont location and for mixtures with low rye component at the Coastal Plain location. The best seeding rate mixture for corn production was 21 kg vetch ha−1 and 47 kg rye ha−1. The vetch-rye mixture can scavenge potentially leachable N, while maintaining corn yields by adding fixed N to the cropping system.