Companies all release their earnings at different times due to their individual financial schedules and not all of them will release the earnings report prior to the day of their earnings call. They will usually announce whether or not they will release the earnings report early and you can sign up for their email announcements.
The SEC website or the company websites would be the best choice to find the reports. Usually the company will keep their earnings reports on their website for months and the SEC website will have all of the reports.
