The development of low-cost and highly efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) is a challenging topic in the fuel cells and metal-air batteries field. Herein, a noble metal-free composite consisting of nano-FeCoNi alloy and spinel oxide was successfully prepared through a simple one-step pyrolytic reduction strategy as identified by XRD, TEM, HRTEM, XPS, and other techniques. The effect of the reduction temperatures (700, 850, and 950 °C) on the composite structure as well as its OER/ORR performances was further investigated. It was observed that FeCoNi@Mn2AlO4 was harvested at the temperature of 700 °C, while FeCoNi@MnAl2O4 was finally formed when the reduction temperature was 850 °C and 950 °C. The composites showed comparable electrocatalytic performance to Pt/C in ORR as well as RuO2 in OER. Moreover, all three catalysts showed great potential for bifunctional catalysis while FeCoNi@MnAl2O4-850 with a ΔEgap of 0.75 V, FeCoNi@MnAl2O4-950 with a ΔEgap of 0.77 V, and FeCoNi@Mn2AlO4-700 with a ΔEgap of 0.83 V. Density functional theory (DFT) computations further confirmed the synergistic effect between FeCoNi and MnAl2O4. This work provides a facile approach to prepare an alternative bifunctional composite electrocatalyst for ORR/OER with deep understanding on the structure-performance relationship.