Background: National guidelines, including the National Accreditation Program for Rectal Cancer, recommend initiation of rectal cancer treatment within 60 days of diagnosis; however, the effect of timely treatment initiation on oncologic outcomes is unclear. The purpose of this study was to evaluate the impact on oncologic outcomes of initiation of rectal cancer treatment within 60 days of diagnosis. Methods: This was a retrospective review of stage II/III rectal cancer patients performed using the United States Rectal Cancer Consortium, a collaboration of 6 academic medical centers. Patients with clinical stage II/III rectal cancer who underwent radical resection between January 1, 2010 and December 31, 2018 were included. The primary exposure was treatment initiation, defined as either resection or initiation of chemotherapy or chemoradiotherapy, within 60 days of diagnosis. The primary outcome was disease recurrence, and the secondary outcome was all-cause mortality. Results: A total of 1,031 patients meeting inclusion criteria were included in the analysis. Treatment was initiated within 60 days of diagnosis in 830 patients (80.5%) and after 60 days in 201 patients (20.3%). In multivariable logistic regression, older age, non-White race, and residence greater than 100 miles from the treatment center were significantly associated with delay in treatment beyond 60 days. In survival analysis, 167 patients (16.2%) experienced recurrent disease, and 127 patients (12.3%) died of any cause. In an adjusted model accounting for pathologic staging, treatment sequence, distance to care, age, comorbidities, treatment center, and receipt of adjuvant chemotherapy, neither progression-free survival nor all-cause mortality was significantly associated with timely initiation of therapy with hazard ratios of 1.09 (0.70, 1.69) and 1.03 (0.63, 1.66), respectively. Conclusion: This study found no difference in oncologic outcomes with initiation of treatment beyond 60 days.