All the quotes are from my LonelyPlanet:

**Bulgaria**:

> Camping in the wild (ie outside a camping ground) is technically
> prohibited but normally accepted if you’re discreet and, most impor-
> tantly, do not build wood fires (which attract attention and damage
> the environment).

**Greece:**

> Free (wild) camping is illegal, but the law is not always strictly
> enforced and some areas are more tolerant and renowned for it, espe-
> cially along the south coast. It is wise to ask around.

For **Macedonia** and **Albania** I could only find a general Western Balkans quote:

> Camping in the wild is usually illegal; ask locals about the
> situation before you pitch your tent on a beach or in an open field.