A high-repetition rate master oscillator power amplifier pumped with laser diodes (LDs) is reported. An injection seeding single-frequency electro-optical Q-switched Nd:YAG laser is used as an oscillator, and a conductively cooled Nd:YAG zigzag slab with a bounce-pumped architecture is utilized as a power amplifier. Pulse energies of over 800 mJ at 1 064 nm and 400 mJ at 532 nm, corresponding to average powers of 200 and 100W, respectively, are achieved with a 12.6-ns pulse width at 250 Hz. Output frequency fluctuations and single-frequency operation are further monitored. Experimental results reveal that the proposed system, which features a single-pass amplified configuration, is a promising design for space-based applications.