I'm not sure what you mean, but if you mean "when Christians started to take over large parts of formerly Muslim Spain" in about the 12th century, then I wrote about it here and noted that at that point, Christian kingdoms and societies were often offering less restrictions and better quality of life for Jews than the restrictive Almoravid and Almohad rulers of Muslim Spain did.

If you mean "when the Reconquista was completed in 1492" then of course the easy answer is that they were immediately expelled.