Yes, leaving your job and losing eligibility for job-based health coverage will trigger a special enrollment opportunity for Marketplace coverage that lasts for 60 days. You can apply for Marketplace health plans and (depending on your income) for premium tax credits and cost sharing reductions during that period to determine your eligibility. If you enroll in COBRA coverage through your former employer, however, you will need to wait until the next Marketplace Open Enrollment period if you want to switch to a Marketplace plan. You may want to look at your Marketplace options before enrolling in COBRA.