USCIS rarely denies an O or P petition outright. If it has concerns, it will typically send a Request for Evidence. If it then decides to deny the case, it may issue a Notice of Intent to Deny (NOID), if the decision will be based on information not submitted by the petitioner, or simply a Notice of Denial that will inform you of certain rights of appeal. As a general rule, appeals take too long and are expensive. Instead, if you feel you have a meritorious case, consider re-filing the petition as a new case (though you should inform USCIS of the prior denial and file number.
At least with USCIS, an appeal is theoretically possible. Remember that no such appeal is available at the next stage of processing if a consulate issues a visa denial, except if the consulate has erred as a matter of law, which they rarely do. Nor is there an appeal from decisions to deny entry by U.S. Customs and Border Protection (CBP).
In a July 13, 2018 memorandum, USCIS announced a change in policy whereby, effective September 11, 2018, adjudicators at the service centers will have “full discretion” to deny visa petitions without first issuing an RFE or a Notice of Intent to Deny (NOID). Although previously adjudicators were required to first issue an RFE or NOID except in extreme cases in which a petition is clearly deniable or the petitioner has requested the wrong category without any possibility of approval, this is no longer going to be the case and it will be at an adjudicator’s discretion whether a petition it deems to be insufficient will result in an immediate denial or whether it will issue an RFE or NOID to allow the petitioner to respond.
The memorandum states:
This policy is intended to discourage frivolous or substantially incomplete filings used as “placeholder” filings and encourage applicants, petitioners, and requestors to be diligent in collecting and submitting required evidence. It is not intended to penalize filers for innocent mistakes or misunderstandings of evidentiary requirements.
However, it also includes the following as an example of a possible denial:
Cases where the regulations, the statute, or form instructions require the submission of an official document or other form or evidence establishing eligibility at the time of filing and there is no submission.
In light of this change in policy, petitioners will need to be even more careful when assembling the required elements of a visa petition.