Olise left Palace two years ago for Bayern and is now rated in the €150m class amid interest from Liverpool and Real Madrid.
Ahead of Palace's Europa Conference League quarterfinal first-leg clash with Fiorentina, Glasner was asked about the France international.
He said: "I watched yesterday's game against Real Madrid. It was a great game to watch and he was outstanding. I think his entire season is really incredible.
"But I'm not surprised and I think he's still not at his ceiling.
"He can still do better. It's great to watch these players and it's not just him. And it's not just him. I think it was Monday when Marc Guéhi had a day off so he visited the Training Ground.
"I think it's a good sign that the players who left Palace are always enjoying coming back to the Training Ground and visiting the players, visiting the staff. So again, until now, it has been a really a great week here."