Here is an excellent website concerning the OSS Operational Groups that is a good resource. It has descriptions of the different missions in Italy, Greece, Yugoslavia, Norway, France, and China; personnel rosters; and a memoir of one OG soldier's experience during WW2 including his two missions: the first in occupied France and the second in China.

The French mission:

There are five of us in the belly of the B-24 Bomber, parachutes on, gear and side arms in place. Our rifles are secured in the containers in the bomb bay. We aren't the only plane heading for France; four other B-24's are in the formation. We are all at 10,000 feet headed for the drop zone into our assigned area at Eguzon, France, 400 miles behind German lines. Our assignment—to work with the French Underground, called the Maquis or F.F.I. [French Forces of the Interior]; first, to capture a hydro-electric plant, then to harass the Germans, and also to collect intelligence to be radioed back to London Headquarters. The French are expecting us because our contact has been there for several months making plans to receive us. His code name is "Hugh". It was the night of August 14th, 1944 and we had been sent to support operation "Anvil"—the southern invasion of France.
The China mission:

This mission was to formulate, train, and equip a detachment of 20 Chinese Commando Units that could work behind the Japanese lines. Meetings had already taken place in January of 1945, just two months before our arrival, between Col. Cox, of the O.S.S., General Wedemeyer and General Chaing-Kai-Shek. These three agreed that well trained Chinese, with the help of combat veteran Americans, could work effectively behind Japanese lines to extract intelligence and thwart the work of the enemy. It was interesting to learn that the army high command kept fighting us, thinking that the regular army troops could do this job. We were specialized in this field and had the know-how to carry it off...

Our assignment in China was completely different from that in France. In France we jumped into an existing underground network that was already functioning. What we became was the catalyst, providing the means and the technique to make it operate effectively and gathering the intelligence necessary to help the Allied invasion forces. In China we had to start from square one to recruit, train and operate an underground espionage group to function behind enemy lines...