The 17-year-old has signed a one-and-a-half-year deal which will see him turn professional with the Cherries in July after finishing the season with his current club and taking his A-levels.
Cornick, who can play up front or as a winger, scored in a development game during his week-long stay with the npower League One side back in November.
Manager Eddie Howe told the Daily Echo: "I think he has got raw attributes. He has got pace, good feet and an eye for goal - which are good qualities to have.
"It is very much a case of a year for Harry to see if he can make a career in the game. We are not trying to build him up at this stage.
"I think it is a risk worth taking from our point of view and I think it is a risk worth taking from his point of view that he gives a year to professional football to see if he can develop a career.
"He does have the raw attributes but he does need a lot of work and dedication to this sport now to see if he can make a go of it."
- Sports & Recreation