The 18-year-old, who has also had a spell with the Siena youth team, will spend the rest of the season at the second-tier Italian club, who are currently bottom of the league
The striker made his first-team debut in a friendly against Stevenage in July but is yet to break into Andre Villas-Boas's plans at Premier League level.
Coulibaly was voted Ivory Coast's Young Player of the Year in 2011 after he netted an astonishing nine goals in only four games in the Under-17s World Cup.
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Grosseto currently find themselves at the bottom of the league in Serie B, 11 points away from safety.