Importance: Despite the substantial health and financial burdens of smoking and the availability of effective, evidence-based interventions in primary care settings, few smokers and physicians use these strategies for smoking cessation. Objective: To evaluate whether electronic outreach to smokers with embedded asynchronous care increases the number of quit attempts and explore the roles of the message sender (ie, primary care physician [PCP] vs health care system) and patient-related characteristics. Design, Setting, and Participants: This quality improvement randomized clinical trial was designed to measure 2 factors: (1) electronic outreach messaging with and without a survey link to asynchronous care and (2) messaging by a personal PCP or health system. The study was conducted within the electronic health record and portal messaging platform of a large health system in the South Central US. Participants were adult patients 18 years or older who were designated as smokers in their electronic health records. Data were collected from January 13 to February 24, 2020, with participating PCPs surveyed in July 2020. Interventions: Portal messages encouraging a quit attempt and offering physician assistance were sent to smokers who were randomly selected and assigned to 1 of 4 conditions (message with or without embedded asynchronous care and PCP or system as sender). Half of the messages contained an invitation to come to clinics and the other half contained a link to access asynchronous care. Main Outcomes and Measures: The primary outcome was electronic health record-documented quit attempts (1 indicates quit attempt; 0, no quit attempt), which were tracked 30 days after the electronic outreach. Secondary outcomes included physician perceptions of the electronic outreach intervention, using a 5-point scale to assess perceptions of workload, comfort with providing medication from survey information, and further interest in the program 6 months after the intervention. Results: A total of 188 participants (99 women [52.4%] and 89 men [47.3%]) with mean (SD) age of 55.2 (13.9) years were randomized to 1 of 4 conditions. Group 1 (n = 46) received a message from the PCP without a link to the survey; group 2 (n = 48) received a message from the PCP with a link to asynchronous care in the form of the survey. Group 3 (n = 47) received a message from the health system without a link to the survey; group 4 (n = 47) received a message from the health system with a link to the survey. No statistically significant difference in documented quite attempts was found among the 4 study groups. There was also no statistically significant difference in quit attempts between the group that received the asynchronous care survey link and the group that did not (odds ratio, 2.50 [95% CI, 0.72-8.72]). However, the quit attempt rate for those with asynchronous care offered (9 of 95 [9.5%]) was more than double the quit attempt rate for those with in-person care offered (4 of 93 [4.3%]). Conclusions and Relevance: This quality improvement randomized clinical trial did not find a statistically significant difference in physician-assisted quit attempts among patients who received electronic with asynchronous care vs those who received outreach alone, regardless of whether the message source was a PCP or a health system. However, the program engaged patients in difficult-to-reach rural areas as well as younger patients. Trial Registration: ClinicalTrials.gov Identifier: NCT05172219.