Is there Scriptural basis for the belief in so called "free will?"Yes, very much so. God told Adam and Eve not to eat from the tree of Life, but they did. They used their "Free Will" to decide to go contrary to what God commanded them
When Moses brought the word of the Lord to the people (Deut 30:15-20)... "See, I have set before you today life and prosperity, death and adversity. If you obey the commandments of the Lord your God that I am commanding you today, by loving the Lord your God, walking in his ways, and observing his commandments, decrees, and ordinances, then you shall live and become numerous, and the Lord your God will bless you in the land that you are entering to possess. But if your heart turns away and you do not hear, but are led astray to bow down to other gods and serve them, I declare to you today that you shall perish; you shall not live long in the land that you are crossing the Jordan to enter and possess. I call heaven and earth to witness against you today that I have set before you life and death, blessings and curses. Choose life so that you and your descendants may live, loving the Lord your God, obeying him, and holding fast to him; for that means life to you and length of days, so that you may live in the land that the Lord swore to give to your ancestors, to Abraham, to Isaac, and to Jacob."
Also, read Joshua 24: 14-15.... "Now therefore revere the Lord, and serve him in sincerity and in faithfulness; put away the gods that your ancestors served beyond the River and in Egypt, and serve the Lord. Now if you are unwilling to serve the Lord, choose this day whom you will serve, whether the gods your ancestors served in the region beyond the River or the gods of the Amorites in whose land you are living; but as for me and my household, we will serve the Lord."
Matthew 7:13.... "Enter through the narrow gate; for the gate is wide and the road is easy that leads to destruction, and there are many who choose to take it."
There are many other places as well