County manager Derek Adams told his club website: "He's a player with top-flight experience who can cover several positions in the midfield."
Corcoran previously played for St Mirren and had two spells at Hamilton.
"Working with a relatively small squad, it's great for me as a manager to know that I have options like that - a versatile player who has a wealth of experience at the highest level," said Adams.
There has been absolutely no fall out between the club and Mark
Partick Thistle manager Ian McCall
Corcoran made 35 appearances during his single season in Glasgow with Thistle.
Partick manager Ian McCall told his club website: "I thought Mark did well for us in the first half of last season but faded in the second half of the season.
"There has been absolutely no fall out between the club and Mark and he leaves Firhill with the best wishes of all."
Source: BBC Sport
Source: BBC Sport