When dividing a polynomial by another polynomial, the degree of the quotient is the difference between the degrees of the numerator and the denominator.
The degree of \( p(x) = x^4 + 2x^3 - 17x^2 - 4x + 30 \) is 4, and the degree of \( q(x) = x^2 + 2x - 15 \) is 2.
Thus, the degree of the quotient is:
\[
4 - 2 = 2.
\]
Thus, the correct answer is \( \boxed{2} \).