Oracy activities are superb for stretching high attaining students, alongside the routine practice of expecting high quality verbal responses in class. Try Soapbox Day - where students give their personal own five minute speech.
Get students to interview one another or adopt a panel style/chat show activity centred around key ideas.
Another idea is to get a group of students or lead learners to explain a concept or demonstration to the class. Get them to use props/white boards or iPads.
Further ideas can be found here: https://www.nace.co.uk/blog/5-reasons-teach-oracy-skills-classroom