Can I apply for a contract on an OPT visa?

On OPT, a student is allowed to work in the field related to the schooling major. I am not quite sure what you mean “apply for a contract”, but if you mean self-employment, that is also allowed in your field of study. Due to the limitations of the Lawyers.com Forums, Alan Lee & Arthur Lee, Esqs.’ (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.