Photonic resonators provide compact frequency references for laser stabilization and precision metrology. Their frequency stability, however, is fundamentally limited by the environmental sensitivity of the resonator material. We explore second-harmonic (SH) stabilization in photonic resonators, which uses the interplay of dispersive mode structure and energy conservation in second-harmonic generation to counter frequency drift. Operationally, we lock two lasers to resonator modes separated by an octave in frequency and compare them through second-harmonic generation. The resulting microwave frequency offset of the lasers, which we refer to as the SH signal ($f_{SH}$), maps changes in the absolute optical frequency of the resonator-stabilized laser to an electronic signal. We characterize this mapping by comparing the optical frequency inferred from $f_{SH}$ with an out-of-loop optical reference, demonstrating accurate tracking of frequency drift. These results show that nonlinear energy conservation supports precision frequency metrology in dispersive resonators.