From the official FAQ: https://fallout.bethesda.net/faqQ: WHEN AND ON WHAT PLATFORMS WILL THE FALLOUT 76 B.E.T.A. BE AVAILABLE?
A: The B.E.T.A. will be available on Xbox One, PlayStation 4, and on PC (via Bethesda.net). Stay tuned for exact timing for each platform here and @Fallout on Facebook, Twitter, and Instagram. Please note that the B.E.T.A. for Xbox One will begin first, followed by other platforms.