ImportanceStay-at-home orders, site closures, staffing shortages, and competing COVID-19 testing and treatment needs all potentially decreased primary care access and quality during the COVID-19 pandemic. These challenges may have especially affected federally qualified health centers (FQHCs), which serve patients with low income nationwide.ObjectiveTo examine changes in FQHCs’ quality-of-care measures and visit volumes in 2020 to 2021 vs prepandemic.Design, Setting, and ParticipantsThis cohort study used a census of US FQHCs to calculate changes in outcomes between 2016 and 2021 using generalized estimating equations.Main Outcomes and MeasuresTwelve quality-of-care measures and 41 visit types based on diagnoses and services rendered, measured at the FQHC-year level.ResultsA total of 1037 FQHCs were included, representing 26.6 million patients (63% 18-64 years old; 56% female) in 2021. Despite upward trajectories for most measures prepandemic, the percentage of patients served by FQHCs receiving recommended care or achieving recommended clinical thresholds showed a statistically significant decrease between 2019 and 2020 for 10 of 12 quality measures. For example, declines were observed for cervical cancer screening (−3.8 percentage points [pp]; 95% CI, −4.3 to −3.2 pp), depression screening (−7.0 pp; 95% CI, −8.0 to −5.9 pp), and blood pressure control in patients with hypertension (−6.5 pp; 95% CI, −7.0 to −6.0 pp). By 2021, only 1 of these 10 measures returned to 2019 levels. From 2019 to 2020, 28 of 41 visit types showed a statistically significant decrease, including immunizations (incidence rate ratio [IRR], 0.76; 95% CI, 0.73-0.78), oral examinations (IRR, 0.61; 95% CI, 0.59-0.63), and supervision of infant or child health (IRR, 0.87; 95% CI, 0.85-0.89); 11 of these 28 visits approximated or exceeded prepandemic rates by 2021, while 17 remained below prepandemic rates. Five visit types increased in 2020, including substance use disorder (IRR, 1.07; 95% CI, 1.02-1.11), depression (IRR, 1.06; 95% CI, 1.03-1.09), and anxiety (IRR, 1.16; 95% CI, 1.14-1.19); all 5 continued to increase in 2021.Conclusions and RelevanceIn this cohort study of US FQHCs, nearly all quality measures declined during the first year of the COVID-19 pandemic, with most declines persisting through 2021. Similarly, most visit types declined in 2020; 60% of these remained below prepandemic levels in 2021. By contrast, mental health and substance use visits increased in both years. The pandemic led to forgone care and likely exacerbated behavioral health needs. As such, FQHCs need sustained federal funding to expand service capacity, staffing, and patient outreach. Quality reporting and value-based care models must also adapt to the pandemic’s influence on quality measures.