Scrum-half Harrison, wing Hurrell and centre Forsyth will be joined in the matchday squad to face Tucuman Under-18s by Tigers colleague Joe Cobden who has been selected among the replacements.
The match is the first of four for Englands tourists and they arrived in South America on the back of a Grand Slam of victories in the Six Nations Festival this season.
England Under-18s head coach John Fletcher said: We know Tucuman will be a very physical side, but we are looking forward to our first game and getting this tour started.
England Under-18s
15 Jack Wallace (London Wasps/RGS High Wycombe)
14 Marcus Watson (London Irish/St Georges College)
13 Andy Forsyth (Leicester Tigers/QEGS Wakefield)
12 Owen Farrell (Saracens/St Georges)
11 Will Hurrell (Leicester Tigers/Queen Elizabeth)
10 Freddie Burns (Gloucester Rugby/Bath College)
9 Sam Harrison (Leicester Tigers/John Cleveland College)
1 Joe Marler (Harlequins, captain)
2 Jamie George (Saracens/Haileybury)
3 Mako Vunipola (Bristol Rugby/Millfield)
4 Tom Holmes (Sale Sharks/Sandbach)
5 James Gaskell (Sale Sharks/Sandbach)
6 Will Welch (Newcastle Falcons/RGS Newcastle)
7 Joe Barker (Leeds Carnegie/QEGS Wakefield)
8 Jamie Gibson (London Irish/Marlborough College)
Replacements
16 David Blackwell (Gloucester Rugby/Hartpury)
17 Peter Austin (London Irish/Worthing College)
18 Joe Quinn (Leeds Carnegie/St Wilfred's School)
19 Sam Jones (London Wasps/Aylesbury Grammar)
20 Sam Edgerley (London Irish/Wellington College)
21 Joe Cobden (Leicester Tigers/King Edward VI Lichfield)
22 Rory Clegg (Newcastle Falcons/Barnard Castle)
23 Jordi Pasqualin (Gloucester Rugby/The Kings School)