Although there are many points in common between Osho's teaching and the Buddha's, there are some subtle differences. In particular, Osho talks about self-realization, while the Buddha addresses the end of suffering:
MN10:2.1: “Mendicants, the four kinds of mindfulness meditation are the path to convergence. They are in order to purify sentient beings, to get past sorrow and crying, to make an end of pain and sadness, to end the cycle of suffering, and to realize extinguishment.
MN10:3.1: What four?
MN10:3.2: It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.3: They meditate observing an aspect of feelings—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.4: They meditate observing an aspect of the mind—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.5: They meditate observing an aspect of principles—keen, aware, and mindful, rid of desire and aversion for the world.
The Buddha also gives a clear warning about wrong immersion. Not all meditation is right. Some meditation is wrong:
AN10.119:13.1: ‘Wrong immersion has a bad result
AN10.119:13.2: in both this life and the next.’
I learned a lot reading Osho's books, but I had questions left unanswered until I read the suttas. And one sutta in particular answered a lot of my questions. In MN8, the Buddha talks about self-effacement, not self-realization. In MN8, the Buddha explains the importance of ethics:
MN8:10.1: It’s possible that some mendicant, going totally beyond the dimension of infinite consciousness, aware that ‘there is nothing at all’, might enter and remain in the dimension of nothingness.
MN8:10.2: They might think
MN8:10.3: they’re practicing self-effacement.
MN8:10.4: But in the training of the Noble One these are not called ‘self-effacement’;
MN8:10.5: they’re called ‘peaceful meditations’.
And in his teaching to Venerable Mahācunda, the Buddha simply says:
MN8:12.2: ‘Others will be cruel, but here we will not be cruel.’
Right immersion requires a basis in ethics, and Buddhist ethics are very subtle, deserving careful study. Without ethics, we fall into wrong immersion, wrong knowledge and wrong freedom.
MN8:12.19: ‘Others will have wrong immersion, but here we will have right immersion.’
MN8:12.20: ‘Others will have wrong knowledge, but here we will have right knowledge.’
MN8:12.21: ‘Others will have wrong freedom, but here we will have right freedom.’
Perhaps the question we might ask ourselves is not "is this self-realization?". Perhaps we might better ask "is this right immersion?" And to answer THAT question, we would need to examine our entire practice for right view, right thought, right speech, right action, right livelihood, right effort, right mindfulness, right immersion and right knowledge.