I've been on the interviewing side at EY (as an external assessor brought in for panel rounds) and done the EY behavioral loop myself as a candidate years ago. Here's what's actually driving these questions.
EY organizes its behavioral competencies around a framework called EY Badges and their broader values: exceptional client service, teaming, inclusiveness, integrity, and 'building a better working world.' That last phrase sounds like marketing but it shows up in interview scoring rubrics in ways candidates don't expect.
The questions you will almost certainly face: Tell me about a time you had to work with someone who had a very different working style. (Teaming.) Describe a situation where you had to deliver difficult news to a client or stakeholder. (Client service + integrity.) Give me an example of leading through ambiguity. (Adaptability, especially relevant for consulting.) Tell me about a time you identified an opportunity to improve a process or outcome. (Innovation within structure.) Describe a situation where there was a conflict within your team. How did you handle it? (Teaming + maturity.)
A few things make EY behavioral interviews distinct from tech company ones. First, they weight client and stakeholder communication heavily, even for tech roles. Your STAR answers should include a stakeholder who is not a peer engineer whenever possible. Second, the 'better working world' angle comes up: they do ask about social impact or community involvement, not as a gotcha, more as a tie-breaker signal. Third, the interviewers are often trained to push back once: 'what would you have done differently?' or 'what was the outcome?' Be ready to extend your answer.
Practical prep: EY publishes their global values online. Read them once, not to memorize, but to understand the lens. Then map 3-4 strong STAR stories you have that each touch two or three of those values at once. You don't need ten different stories. You need four really good ones that stretch.