The objective of this research was to conduct a preliminary study to determine if solubles syrup from a microbially-enhanced soy protein (MSP) production process has potential as a supplement for growing dairy heifers. A 6-wk randomized complete block design study was conducted using 14 Holstein and 4 Brown Swiss heifers [310 ± 16.4 d of age; body weight (BW) 337.6 ± 33 kg] to evaluate effects of diet on growth performance. Treatments were: 1) a control total mixed ration (TMR) with corn, soybean meal and distillers dried grains with solubles as concentrate ingredients (CON) and 2) a TMR with 6.5% MSP solubles syrup (DM basis) in partial replacement of soybean meal and corn (SYP). Both diets contained 34% corn silage, 35% grass hay, and 2.6% mineral mix and were isonitrogenous and isocaloric. Heifers were individually fed TMR for ad libitum intakes using a Calan gate feeding system. Frame sizes, BW, and body condition score (BCS) were measured on 2 d during wk 0, 2, 4, and 6 of the feeding period. Rumen fluid was sampled via esophageal tube 2 d during wk 0 and 6 and 1 d during wk 2 and 4 at 4 h post-feeding. Data were analyzed with MIXED procedures with repeated measures in SAS 9.4. There were no interactions of treatment by wk for any of the parameters evaluated. Treatments had similar (P > 0.05) DMI (9.9, and 9.7 kg/d for CON and SYP, respectively; SEM = 0.49), body weight (366.2, and 365.3 kg; SEM = 2.73), ADG (1.00 and 0.97 kg/d; SEM = 0.09), gain:feed (0.11, and 0.13; SEM = 0.02) and BCS (3.10, and 3.10; SEM = 0.30). Frame growth measures including hip height (134.9, and 131.3 cm; SEM = 1.92), withers height (131.0, and 131.0 cm; SEM = 0.40), heart girth (156.7, and 160.7 cm; SEM = 3.21), body length (124.5 and 129.2 cm; SEM = 2.64) and hip width (41.8 and 41.7; SEM = 0.38) and their rates of change were the same between treatments. Rumen pH (6.9, and 6.9; SEM = 0.072) was not affected by treatment. Results demonstrated that partially replacing soybean meal and ground corn with MSP solubles syrup maintained heifer growth performance with a similar gain:feed.