The 19-year-old progressed through Albion’s youth ranks before breaking into Simon Rusk’s under-23 squad last season after making more than 30 appearances for the club’s under-18s.
McGill had a loan spell with non-league Greenwich Borough but now links up with Crawley, who are 15th in League Two.
Under-23s assistant manager Shannon Ruth said, “This is another stage in Tom’s development to go and play League 2 football and learn and improve through the different situations he will experience in the next few months.
“We will be monitoring his progress carefully and we wish him well.”