Make sure you are honest in the reading of these verses. The context of these verse are found in verse 3 in which you left out. Let's read:
3 Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly places in Christ:
4 According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
5 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will,
6 To the praise of the glory of his grace, wherein he hath made us accepted in the beloved.
You see, the context are the spiritual blessings that God has given in Christ. The very next word in verse 4 is according...you see, what God has given those in Him, in Christ is in accordance to what God had chosen to give before the foundation of the world to those who would be found in Christ. It's all about the heavenly blessings that are found in Christ. It does not say, as Calvinists like to read, we were chosen to be in him before the foundation of the world. No sir.
Verse 5, Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will,...who has God predestinated? Us, those who are in Christ. What has God predestinated us for? The adoption, which is the redemption of our bodies, Romans 8:23.
You see, before the foundation of the world, Jesus Christ was chosen to be the means by which God would bestow heavenly blessings upon. How can man take part of these heavenly blessings? You've got to get in Christ through the gospel. Once in Christ, you are predestined for these blessings which includes the adoption. They are future blessings for the believer who is in Christ.