Sporting's club president Peter Vaz was upset with the way his team was performing.
"Oscar will be our new chief coach and take charge of the training session tomorrow," said Vaz.
Sporting Clube suffered their third consecutive defeat and now have seven points from nine matches.
Oscar, 35, has been around in India for a while and has been involved in a couple of academies cross the country.
His latest assignment was with the SPT Academy in Bangalore.
He has donned colours for CElta de Vigo in the Spanish second division and trained the under-14 squad of the same team, which now plays in the Spanish La Liga.
Oscar has also attained a Bachelor of Business Administration degree from the University of Vigo in Spain.
Vaz said Ekendra Singh will continue to be involved with the coaching staff and assist Oscar, while Alex Alvares will be the technical director.
