@cyrus - OPT is still F1, so the same rule applies to you. F1 students are supposed to file 1040NR and 8843 for the first 5 years (NR= non resident), and 1040 (the same form that citizens use) starting 6th year. If you are asking this question, you probably have been filing 1040 all these years. Look at my answer above to see how this might affect you in the future.