Background: Adjuvant CRT with high-dose cisplatin remains standard treatment for OCSCC with high risk pathologic features of positive surgical margins (SM+) and/or extranodal extension (ENE). High-dose cisplatin is associated with significant toxicities, and alternative dosing schedules or treatments are used. We evaluated outcomes associated with different systemic therapies concurrent with RT and the effect of cumulative dosing of cisplatin. Methods: An IRB-approved collaborative database of patients (pts) with primary OCSCC (Stage I-IVB AJCC 7th edition) treated with primary surgical resection between 1/1/2005 and 1/1/2015 with or without adjuvant therapy was established from 6 academic institutions. Pts were categorized by systemic therapy received, and resultant groups compared for demographic data, pathologic features, and outcomes by t-test and Chi-squared tests. Kaplan-Meier curves, log-rank p-values, and multivariate analysis (MVA) for disease free survival (DFS) and freedom from metastatic disease (DM). Results: From a total sample size of 1282 pts, 196 pts were identified with high risk features (SM+, ENE) who were treated with adjuvant CRT. Median age was 56 years, 63.3% of pts were men, 81.1% were Caucasian, 70.9% had significant tobacco history. 35.7% of pts had SM+, 82.7% ENE, 65.3% with perineural invasion (PNI), 49% had lymphovascular space invasion (LVSI). There was a trend associating higher cisplatin dose delivered with improved locoregional control, DM, and overall survival (OS) (p-values 0.131, 0.084, and 0.187, respectively). DFS was significantly better with higher cisplatin dose (HR = 0.95 per 100 mg/m² increase in cisplatin). Administration schedule of cisplatin (weekly versus high-dose) was not significantly associated with DFS. On MVA, PNI and higher cisplatin dose remained statistically significant for DFS (p < 0.001 and 0.007). Median OS by cisplatin dose was 10.5 ( < 200 mg/m²) vs. 20.8 months ( > / = 200 mg/m²). Conclusions: This multi-institutional analysis demonstrated cumulative cisplatin dose > / = 200 mg/m² was associated with improved DFS in high risk resected OCSCC pts. It remains unclear by this analysis if cisplatin administration schedule has any prognostic implication. Further study is warranted to elucidate the optimal cisplatin schedule for this population.