The 21-year-old initially joined Trinity in January for a month which was extended and now he will remain at the Northolme until the end of April.
Former Sheffield Wednesday trainee Beatson swapped life with Trinity for Boston in May.
Having spent the first season of his senior career at The Northolme, Beatson moved across Lincolnshire alongside team-mate George Willis.
Beatson, who is capable of playing at centre-half or left-back, made fifteen starts and one substitute appearance for the Pilgrims this season.
And since returning to Trinity, has added eleven starts to his tally.