It is not required to have a fully executed, written contract with your employer for the O-Visa petition.
You can submit a deal memo, group of emails or other writing that meets the requirements of a basic contract
However, the evidence must detail the following:
- an offer
- Acceptance
- the payment or other compensation
- the position
- employment address
- the job duties
- hours
As long as those are outlined in the petition, the written contract is waived.