Rydberg series of msns and msnd configurations of Be (m=2) and Mg (m=3) were investigated between principal quantum numbers 10 ≤ n ≤ 70. The Rydberg states were populated using stepwise excitation or direct two-photon transitions with frequency doubled light (235 nm ≤ λ < 330 nm) from pulsed dye lasers. The excited Rydberg atoms were detected with a space charge limited thermionic diode. An analysis of the Rydberg series both in Be and Mg by means of multi-channel quantum-defect theory (MQDT) results in the determination of mp2 1D2 admixtures in msnd 1D2 states.