This is how Grenz typified evidentialist apologetics:
Conservatives disagreed vehemently with what they saw as a blatant attack on the integrity of the Bible. Nevertheless, with the same zeal as their liberal antagonists, they also sought to incorporate faith in a realm ruled by reason. To this end, they devised what is known as evidentialist Christian apologetics. This strategy shows how scientific findings support or even confirm the truths of Christianity.
He then goes on to cite Josh McDowell as a typical example of this kind of apologetics. There is a lot to deal with in this quote. First, Grenz is certainly right that theological conservatives reacted strongly to the liberal take on biblical inerrancy, miracles, and so forth. In many respects it was that reaction which gave rise to the fundamentalism of the early twentieth century.
Secondly, I am not so sure that the assessment “they also sought to incorporate faith in a realm ruled by reason” is accurate in this context. I think the problem with this statement harkens back to the distinction between Rationalism and the use of reason. Grenz may be equivocating at this point in order to argue that evidentialist apologetics of the last century is an extension of Rationalism. Evidentialist apologetics certainly, and unashamedly, makes use of reason in all its traditional forms, but it does not, in its best incarnations, agree to the tenants of Rationalism.
In support of my point, I would like to observe that most of what passes for evidentialist apologetics now is an extension of Medieval theology, most notably the work of Anselm and Aquinas. Many of the standard arguments which now comprise the core of philosophy of religion and Christian apologetics are repetitions of and modifications upon their work. What Grenz is associating with and attributing to the eighteenth and nineteenth centuries in actuality extends back much further than that. So to say, “they devised what is known as evidentialist Christian apologetics,” may be overstated.
Now it can be objected that even though the roots of contemporary evidentialism extend back through the Middle Ages, it may be that Aquinas and Anselm presaged the worst parts of the Enlightenment project. If one were to so argue, I would think that the equivocation clarification again comes into play. It may be true that Aquinas was extremely rational, but one simply cannot level the charge of “rationalistic” against him. Even though Aquinas had his “Five Ways” (the five arguments for the existence of God based on general revelation), he was also clear about the mystery of specific revelation. So again, Medieval theology may have been deliberately rational, but it was not in step with Rationalism.