Background: There has been a significant decline in office visits and cancer screening interventions such as mammograms and colonoscopies during the COVID-19 pandemic. The aim of this study is to analyze treatment patterns and to identify if there was also a delay in time to treatment for breast and colorectal cancers diagnosed during the pandemic. Methods: We utilized a dataset linking the institutional tumor registry and electronic health records from a large ambulatory group practice in Northern California. We analyzed data from 1,047 patients with newly diagnosed breast and colorectal cancers between 1/2019 and 8/2020 who received care at Sutter Health-Palo Alto Medical Foundation until 12/2020. We performed a T-test to examine whether patterns of treatment status (surgery vs chemotherapy vs neither) and time-to-treatment are different in pre-COVID vs pandemic eras. Results: The proportion of patients who did not receive surgery or chemotherapy during the pandemic was significantly higher, compared to the pre-COVID era (34.5% vs. 13.0%, p < 0.01). Among the breast and colorectal cancer patients who received care, the time to initial treatment did not significantly vary in the pre-COVID (median 34 days, mean 36.8 days) era as compared to during the pandemic (median 30 days, mean 32.2 days) (p = 0.15). There was no difference when accounting for surgery (p = 0.15) vs chemotherapy (p = 0.52) as the initial treatment modality. A statistically significant difference was seen amongst the 888 breast cancer cases identified during the study period, but the mean time to treatment during the pandemic (31 days) was actually shorter than the mean time to treatment identified prior to the pandemic (38 days). This difference in breast cancer time to treatment was mainly driven by a statistically shorter time to surgery (p = 0.04) in the pandemic era with no statistically significant difference in time to chemotherapy following a breast cancer diagnosis in the pandemic era as compared to the pre-COVID era (p = 0.99). Conclusions: There was a significant difference in the number of patients who did not receive surgery or chemotherapy during the pandemic for newly diagnosed breast and colorectal cancers. However, amongst those patients who did receive treatment, there were no significant delays observed in time to initial treatment, regardless of treatment modality.