The afternoon saw Scottish Premiership side the comfortable winners, with goals from McGowan, Ashcroft and Jakubiak the difference.
Kenny Jackett named an eleven which featured four of his five summer signings, as Pratley, Wood, Smyth and Drinan lined up at the Kilmac Stadium.
Captaining the side for the first time, Pratley lined up at centre-back alongside Dan Happe, as Omar Beckles missed out for international duty.
The Scottish Premiership side started the stronger of the two teams, and took the lead after only five minutes.
McGowan found time and space on the edge of the box, and picked out the top right corner with a sweet right footed strike, that Sargeant couldn’t stop.
The O’s grew into the game though, and soon had their first chance after Sotiriou drove infield before finding Matt Young.
Young composed himself and fired a half-volley goalwards, but former O Legzdins made a smart stop from close range.
Soon after a heavy tackle from Dan Happe on Anderson, saw him pick up a booking, in a move that saw McGowan break through.
His right-footed effort looked goal bound, but Sargeant made a fine stop down to his right to deny him.
Soon after, Paul Smyth showed Orient fans watching at home what they could expect from him, as a burst of pace saw hum beat his man and forge a great chance, before firing just wide.
Dundee could have had a second before the break after Sotiriou’s loose ball was swooped n by the Dee, but Dan Happe was on hand to make a heroic goal line block onto the bar, when it seemed to be a certain goal.
Straight after the break, Dundee doubled their lead as Jakubiak converted from close range, after good work from his teammate caught Orient unawares.
Soon after, they had a third, as a ball into the box was met with a well timed volley from Ashcroft, who was able to nestle it into the bottom corner from 12 yards.
Orient should have had one back after great work from Wood saw his deep ball played back into the path of Drinan – but his goalbound effort was blocked onto the post, and Dundee cleared.
Soon after this, Kenny Jackett rang the changes, with all five of the academy players in the squad joining the action, alongside Ogie, Papadopoulos, Sweeney and Byrne.
The youthful side settled into the game well and, despite their relative inexperience, were able to contain Dundee and work the ball nicely in passages.
The game came to a close, and although a disappointing scoreline, a valuable workout for The O’s and experience for the academy prospects.
Dundee: Legzinds, Kerr, Fontaine, Jakubiak, McGowan, Ashcroft, Elliott, McMullan, Robertson, Anderson, Adam.
Subs: Sharp, Marshall, Sweeney, McGhee, Byrne, McDaid. McCowan. Trialist, Trialist, Trialist.
Leyton Orient: Sargeant (Byrne 60’), Wood (Sweeney 60’), Cisse (Papadopolous 60’), Happe (Eaton 60’), Smyth (Sodje 60’), Clay (Nkrumah 60’), Drinan (Nkrumah 60’), Pratley (c) (Ogie 60’), Sotiriou (Tanga 60’), Young, Kyprianou.
Subs: Kwatchey, Nkrumah, Tanga, Sodje, Eaton, Papadopoulos, Sweeney, Ogie, Byrne (GK)