The Glenavon FC official website reports that the 17-year-old will sign for the Dons once personal terms are agreed, a medical examination is passed and all the necessary paperwork has been completed.
The Dons beat off competition from Championship side Watford for the Portadown-born starlet's signature.
A Belfast newspaper believes that Glenavon have agreed a fee in the region of £15,000 for the player, with future payments coming through add-ons connected to appearances and possible international call-ups.
Stewart broke into the Glenavon first-team during the most recent campaign and is described as one of their shining lights. He started nine games for Glenavon, coming on as substitute in seven. He has scored one goal in those games - a great volley from the edge of the box in a 3-3 draw with Cliftonville in April (see YouTube footage below) - and picked up one yellow card.
A spokesman for Glenavon said: "We wish Sammy every success in his future football career."