Baxter and Gustard have been recruited to fill in for Graham Rowntree and Andy Farrell, who will be on British and Irish Lions duty at the same time England embark on their four-match, two-Test trip to South America.
Lancaster will also be supported by Mike Catt, the attacking skills coach who landed a permanent role in the England set-up after impressing on last summer's tour of South Africa.
Baxter masterminded Exeter's rise from the Championship into the Heineken Cup and he was named Premiership Rugby's coach of the year for the 2011-12 season.
Gustard runs the meanest defence in the Aviva Premiership, with table-topping Saracens having conceded just 17 tries in 18 matches so far this season.
The Rugby Football Union said in a statement: "Exeter Chiefs director of rugby Rob Baxter and Saracens defence and forwards coach Paul Gustard will join the England coaching team for the tour to Argentina in June."
- Sports & Recreation
- Premiership Rugby