It would be acceptable to ask whether an individual was terminated or asked to leave a position in the past two years, and it would be acceptable to ask for the reason. The only problem I can see here would be the very rare situation where someone was terminated for a reason like filing a discrimination complaint or failing to return from a medical/maternity/military leave. This situations should be handled very carefully. One other question you might want to consider: how will you handle situations where an individual was terminated as part of a reduction in the workforce?
You can use this OFCCP audit checklist to ensure you're doing what is required to maintain OFCCP's regulations including VEVRAA, Section 503, and EO 11246. Or request a demo to streamline your compliance and recruiting efforts.