Scripture is clear on that. We are saved by enduring until the end, not being moved away from the faith. So in a since I do believe in OSAS (not how it is taught in your churches of course). But if we are not really saved until we have endured then once we have endured and finished the race entering into eternity as a believer then we will remain saved forever.
Back to the enduring part.
Matthew 24
12 And because iniquity shall abound, the love of many shall wax cold.
13 But he that shall endure unto the end, the same shall be saved
Mark 13:13 And ye shall be hated of all men for my name's sake: but he that shall endure unto the end, the same shall be saved.
Colossians 1
21 And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled
22 In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight:
23 If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;
2nd Timothy 4:7 I have fought a good fight, I have finished my course, I have kept the faith:
Hebrews 3
6 But Christ as a son over his own house; whose house are we, IF we hold fast the confidence and the rejoicing of the hope firm unto the end
14 For we are made partakers of Christ, IF we hold the beginning of our confidence stedfast unto the end;
Revelation 2:26 And he that overcometh, and keepeth my works unto the end, to him will I give power over the nations:
Here are 7 passage of scripture that says we must finish the race/endure until the end to obtain eternal life as Paul says in Philippians 3
Philippians 3
11 If by any means I might attain unto the resurrection of the dead.
12 Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus.
And again in 1st Corinthians
1st Cor 9:27 But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.
Paul knew starting the race meant nothing, but finishing the race brought about eternal life.
I have shown you many passages that says we must endure to be granted eternal life, now you give me one that says starting the race is all we must do.