Uncooked chicken burgers in the oven, thawed, then put into the fridge
They are probably safe to eat, although it's difficult to tell for sure. 

The basic rule is that food should spend no longer than 2 hours in the danger zone between 4 and 60 Celsius. Assuming that it took them less than 2 hours to go from "warm and unfrozen" to fridge temperature (which is below 4 Celsius), they are officially safe to eat. With small food items like burgers, this shouldn't be a problem. It is large pots of food such as soup which may take too long to cool down from just-cooked to fridge temperature, but a hamburger has much less volume.