This study was conducted to evaluate the interaction between the amount of concentrate provided in an AMS and the energy density in a PMR on DMI, milk and milk component yield, and ruminal fermentation. Eight ruminally cannulated Holstein cows (replicated 4 × 4 Latin square), housed in a guided-traffic flow barn, were fed a PMR containing either low (54:46; L-FOR) or a high (63:37; H-FOR) forage to concentrate ratio. Within each PMR, cows were provided to achieve either a low (2 kg/d; L-AMS) or a high (6 kg/d; H-AMS) concentrate in the AMS. Data were analyzed using the mixed model in SAS (version 9.4) with significance declared when P < 0.05. Variation in AMS concentrate intake among days was greater for H-AMS than L-AMS (0.83 vs 0.22 kg/d; P < 0.01), while there were no changes in PMR intake. Total DMI (PMR+AMS) was not affected by treatments, averaging 27 kg/d. Cows fed the H-AMS consumed 3.5 kg less PMR than cows fed L-AMS (P < 0.01), regardless of the PMR energy content. A greater number of voluntary visits were observed in cows fed H-AMS than L-AMS (3.7 vs 3.5; P = 0.02) with a tendency for greater milk yield (39.2 vs 38.0 kg/d; P = 0.10). The L-FOR PMR tended to increase milk yield (39.3 vs 37.9; P = 0.10) compared with H-FOR. Milk protein content was greater for cows fed the H-AMS than the L-AMS (3.25 vs 3.20%; P = 0.04); while, milk fat content tended to be reduced (P = 0.09) with H-AMS compared with L-AMS (3.51 vs 3.64%). Ruminal pH variables were not affected by treatments. However, short-chain fatty acid concentration was greater for cows fed L-FOR PMR and H-AMS than cows fed H-FOR PMR and L-AMS (112.95 vs 108.43 mM; P = 0.03). These data suggest that feeding a greater quantity of concentrate in the AMS increases variability in concentrate consumption but may also improve voluntary visits and milk yield. When considering iso-caloric diets, these results suggest no benefit of providing more concentrate in the AMS.