Wolves teenager Vokes had been linked with a move to Elland Road but Gradel's arrival had been kept under wraps until he was named among the substitutes on Grayson's teamsheet for the 2-1 win on Monday night. Both players will stay with Leeds for an initial month.
Grayson said: "We're delighted to bring in both players. Both lads are still young but they have good quality about them.
"Sam is a highly-rated goalscorer and Max has plenty of pace and both players fit in well to the squad we have here. I'm looking forward to working with them both.
"I'd like to thank Wolves and Leicester for allowing them to come here."