Large zoom/fixed Lenses for Full Frame

No. In Canon there are several zooms and primes covering 300mm that range from consumer to L.

http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup

Sigma also has several zooms and primes covering 300mm.

http://www.sigmaphoto.com/shop/lenses?gclid=CLqHwbWwz7MCFck7MgodBFYAog

Tamron has a 200-500 f/5-6.3, but it doesn't have stabilization.

And lots more of old manual focus Nikon, Pentax, Contax/Yashica, ... that can be easily adapted to EOS.

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Unapologetic Canon Apologist